diff --git a/scala3doc/resources/dotty_res/scripts/fast-navigation-loader.js b/scala3doc/resources/dotty_res/scripts/fast-navigation-loader.js
deleted file mode 100644
index 3b9c5b9b9b57..000000000000
--- a/scala3doc/resources/dotty_res/scripts/fast-navigation-loader.js
+++ /dev/null
@@ -1,55 +0,0 @@
-navigationPageText = fetch(pathToRoot + "navigation.html").then(response => response.text())
-
-window.addEventListener('DOMContentLoaded', () => {
-  navigationPageText.then(data => {
-          document.getElementById("sideMenu").innerHTML = data;
-      }).then(() => {
-      document.querySelectorAll(".overview > a").forEach(link => {
-          link.setAttribute("href", pathToRoot + link.getAttribute("href"));
-      })
-  }).then(() => {
-      document.querySelectorAll(".sideMenuPart").forEach(nav => {
-          if (!nav.classList.contains("hidden")) nav.classList.add("hidden")
-      })
-  }).then(() => {
-      revealNavigationForCurrentPage()
-  })
-
-  /* Smooth scrolling support for going to the top of the page */
-  document.querySelectorAll('.footer a[href^="#"]').forEach(anchor => {
-      anchor.addEventListener('click', function (e) {
-          e.preventDefault();
-
-          document.querySelector(this.getAttribute('href')).scrollIntoView({
-              behavior: 'smooth'
-          });
-      });
-  });
-})
-
-revealNavigationForCurrentPage = () => {
-  let pageIdParts = document.getElementById("content").attributes["pageIds"].value.toString().split("/")
-  let parts = document.querySelectorAll(".sideMenuPart");
-  let found = 0;
-  do {
-      let pageId = pageIdParts.join("/")
-      parts.forEach(part => {
-          if (part.attributes['pageId'].value.indexOf(pageId) !== -1 && found === 0) {
-              found = 1;
-              if (part.classList.contains("hidden")){
-               part.classList.remove("hidden");
-               part.setAttribute('data-active',"");
-              }
-              revealParents(part)
-          }
-      });
-      pageIdParts.pop()
-  } while (pageIdParts.length > 0)
-};
-
-revealParents = (part) => {
-  if (part.classList.contains("sideMenuPart")) {
-      if (part.classList.contains("hidden")) part.classList.remove("hidden");
-      revealParents(part.parentNode)
-  }
-};
\ No newline at end of file
diff --git a/scala3doc/resources/dotty_res/scripts/ux.js b/scala3doc/resources/dotty_res/scripts/ux.js
index 185b2a718d44..2587b8629d54 100644
--- a/scala3doc/resources/dotty_res/scripts/ux.js
+++ b/scala3doc/resources/dotty_res/scripts/ux.js
@@ -15,6 +15,10 @@ window.addEventListener("DOMContentLoaded", () => {
     }
   }
 
+  $("#sideMenu2 span").on('click', function(){
+    $(this).parent().toggleClass("expanded")
+  });
+
 
   if (location.hash) {
     var selected = document.getElementById(location.hash.substring(1));
diff --git a/scala3doc/resources/dotty_res/styles/scalastyle.css b/scala3doc/resources/dotty_res/styles/scalastyle.css
index 6e17a18f45d2..6efd941b2a9d 100644
--- a/scala3doc/resources/dotty_res/styles/scalastyle.css
+++ b/scala3doc/resources/dotty_res/styles/scalastyle.css
@@ -123,12 +123,6 @@ th {
 }
 
 /* Left bar */
-#sideMenu {
-  overflow-y: auto;
-  scrollbar-width: thin;
-  height: 100%;
-  font-size: var(--leftbar-font-size);
-}
 #paneSearch {
   display: none;
 }
@@ -159,63 +153,88 @@ th {
   width: 116px;
 }
 
-.sideMenuPart {
-  padding-left: 1em;
+/* Navigation */
+#sideMenu2 {
+  overflow-y: auto;
+  scrollbar-width: thin;
+  height: 100%;
+  font-size: var(--leftbar-font-size);
+}
+
+/* divs in sidebar represent entry and its children */
+#sideMenu2 div {
+  padding-left: 0.7em;
+  position: relative;
+  display: none;
+}
+
+#sideMenu2 div.expanded {
+  display: block;
+}
+
+/* hide children of hidden entries even if are expanded */
+#sideMenu2 div>div.expanded {
+  display: none;
+}
+
+/* show direct children of currently exmanded node*/
+#sideMenu2 div.expanded>div {
+  display: block;
+}
+
+/* always show top level entry*/
+#sideMenu2>div{
+  display: block;
 }
-.sideMenuPart a {
+
+/* 'a's in side menu represent text of entry with link */
+#sideMenu2 a {
   align-items: center;
   flex: 1;
   overflow-x: hidden;
   overflow-wrap: anywhere;
   color: var(--leftbar-fg);
   margin-right: .5rem;
-  padding: 7px 0;
-}
-.sideMenuPart > .overview {
-  display: flex;
-  align-items: center;
-  position: relative;
-  user-select: none;
-}
-.sideMenuPart > .overview::before {
-  width: var(--side-width);
-  box-sizing: border-box;
-  content: '';
-  top: 0;
-  right: 0;
-  bottom: 0;
-  position: absolute;
-  z-index: 1;
-}
-.sideMenuPart > .overview:hover::before {
-  background: var(--leftbar-hover-bg);
+  padding-top: 3px;
+  padding-bottom: 3px;
+  margin-top: 1px;
+  margin-bottom: 1px;
+  width: 100%;
+  display: block;
+  /* This trick adds selected bachground stratching to the lef side of screen */
+  margin-left: calc(0px - var(--side-width));
+  padding-left: var(--side-width);
+  width: calc(2 * var(--side-width));
 }
-.sideMenuPart > .overview:hover > a {
-  color: var(--leftbar-hover-fg);
+
+#sideMenu2 a::before {
+  margin-left: -12em;
+  width: 12em;
+  background: red;
 }
-.sideMenuPart[data-active] > .overview::before {
+
+#sideMenu2 a.selected {
   background: var(--leftbar-current-bg);
-}
-.sideMenuPart[data-active] > .overview > a  {
   font-weight: bold;
-  color: var(--leftbar-current-fg);
 }
-.sideMenuPart.hidden > .sideMenuPart {
-  height: 0;
-  visibility: hidden;
-}
-.overview a, .overview .navButton {
-  z-index: 3;
+
+#sideMenu2 a:hover {
+  color: var(--leftbar-hover-fg);
+  background: var(--leftbar-hover-bg);
 }
-.sideMenuPart .navButton {
+
+/* spans represent a expand button */
+#sideMenu2 span {
   align-items: center;
-  display: flex;
-  justify-content: flex-end;
-  padding: 7px 10px;
   cursor: pointer;
+  position: absolute;
+  right: 1em;
+  top: 0px;
+  padding: 4px;
 }
-.sideMenuPart .navButtonContent::before {
-  content: "\e905"; /* arrow up */
+
+#sideMenu2 span::before {
+  content: "\e903"; /* arrow down */
   font-family: "dotty-icons" !important;
   font-size: 20px;
   line-height: var(--leftbar-font-size);
@@ -225,10 +244,11 @@ th {
   align-items: center;
   justify-content: center;
 }
-.sideMenuPart.hidden .navButtonContent::before {
-  content: "\e903"; /* arrow down */
+#sideMenu2 .expanded>span::before {
+  content: "\e905"; /* arrow up */
 }
-.sideMenuPart .navButton:hover .navButtonContent::before {
+
+#sideMenu2 .div:hover>span::before {
   color: var(--leftbar-current-bg);
 }
 
@@ -295,7 +315,7 @@ th {
   padding-top: 0;
 }
 
-span[data-unresolved-link].strikethrough, a.strikethrough, div.strikethrough {
+span[data-unresolved-link].deprecated, a.deprecated, div.deprecated {
   text-decoration: line-through;
 }
 .brief {
diff --git a/scala3doc/src/dotty/dokka/DocContext.scala b/scala3doc/src/dotty/dokka/DocContext.scala
index d6752cb4e889..7eb58039d1bd 100644
--- a/scala3doc/src/dotty/dokka/DocContext.scala
+++ b/scala3doc/src/dotty/dokka/DocContext.scala
@@ -69,6 +69,7 @@ extension (r: report.type)
   def warn(m: String, f: File)(using CompilerContext): Unit =
     r.warning(createMessage(m, f, null), sourcePostionFor(f))
 
+case class NavigationNode(name: String, dri: DRI, nested: Seq[NavigationNode])
 
 case class DocContext(args: Scala3doc.Args, compilerContext: CompilerContext)
   extends DokkaConfiguration:
@@ -86,6 +87,9 @@ case class DocContext(args: Scala3doc.Args, compilerContext: CompilerContext)
 
     lazy val displaySourceSets = getSourceSets.toDisplaySourceSet
 
+    // Nasty hack but will get rid of it once we migrate away from dokka renderer
+    var navigationNode: Option[NavigationNode] = None
+
     val logger = new Scala3DocDokkaLogger(using compilerContext)
 
     lazy val staticSiteContext = args.docsRoot.map(path => StaticSiteContext(
diff --git a/scala3doc/src/dotty/dokka/preprocessors/ScalaEmbeddedResourceApppender.scala b/scala3doc/src/dotty/dokka/preprocessors/ScalaEmbeddedResourceApppender.scala
index 650b86856cd1..20e708ae9e02 100644
--- a/scala3doc/src/dotty/dokka/preprocessors/ScalaEmbeddedResourceApppender.scala
+++ b/scala3doc/src/dotty/dokka/preprocessors/ScalaEmbeddedResourceApppender.scala
@@ -37,8 +37,7 @@ class ScalaEmbeddedResourceAppender extends PageTransformer {
           "scripts/components/Input.js",
           "scripts/components/FilterGroup.js",
           "scripts/components/Filter.js",
-          "scripts/data.js",
-          "scripts/fast-navigation-loader.js"
+          "scripts/data.js"
         )).asJava,
         page.getChildren
       )
diff --git a/scala3doc/src/dotty/dokka/site/NavigationCreator.scala b/scala3doc/src/dotty/dokka/site/NavigationCreator.scala
index 2207c59993bf..b3541a4b6ebe 100644
--- a/scala3doc/src/dotty/dokka/site/NavigationCreator.scala
+++ b/scala3doc/src/dotty/dokka/site/NavigationCreator.scala
@@ -1,7 +1,6 @@
 package dotty.dokka
 package site
 
-import org.jetbrains.dokka.base.renderers.html.{NavigationNode, NavigationPage}
 import org.jetbrains.dokka.model.DPackage
 import org.jetbrains.dokka.model.DModule
 import org.jetbrains.dokka.pages._
@@ -11,7 +10,7 @@ import scala.collection.JavaConverters._
 
 class NavigationCreator(using ctx: DocContext) extends PageTransformer:
 
-  private def processApiPages(pages: List[PageNode]): JList[NavigationNode] =
+  private def processApiPages(pages: List[PageNode]): List[NavigationNode] =
     def flatMapPackages(pn: PageNode): List[NavigationNode] =
       def processChildren = pn.getChildren.asScala.flatMap(flatMapPackages).toList
       pn match
@@ -22,8 +21,7 @@ class NavigationCreator(using ctx: DocContext) extends PageTransformer:
           case p: DPackage if p.getName == "<empty>" && p.getChildren.isEmpty =>
             Nil
           case p: DPackage =>
-            val ss = p.getSourceSets.asScala.toSet.toDisplay
-            List(new NavigationNode(p.getName, p.getDri, ss, JList())) ++ processChildren
+            List(new NavigationNode(p.getName, p.getDri, Nil)) ++ processChildren
           case _: DModule =>
             processChildren
           case _ =>
@@ -31,15 +29,13 @@ class NavigationCreator(using ctx: DocContext) extends PageTransformer:
         case _ =>
           Nil
 
-    pages.flatMap(flatMapPackages).sortBy(_.getName).asJava
+    pages.flatMap(flatMapPackages).sortBy(_.name)
 
   private def processStaticPages(input: PageNode)(staticSiteContext: StaticSiteContext) =
     def toNavigationNode(page: StaticPageNode): NavigationNode = NavigationNode(
       page.title(),
       page.getDri.asScala.head,
-      ctx.displaySourceSets,
-      page.getChildren.asScala
-        .collect { case p: StaticPageNode => toNavigationNode(p)}.asJava
+      page.getChildren.asScala.collect { case p: StaticPageNode => toNavigationNode(p) }.toList
     )
 
     def singleContentPage(p: PageNode) =
@@ -49,10 +45,9 @@ class NavigationCreator(using ctx: DocContext) extends PageTransformer:
       if !pageRoot.getDri.contains(topLevelDri) then pageRoot
       else singleContentPage(pageRoot)
     val apiPages = docsRoot.getChildren.asScala.filterNot(_.isInstanceOf[StaticPageNode])
-    val staticPages = staticSiteContext.mainPages.map(toNavigationNode).toList.asJava
+    val staticPages = staticSiteContext.mainPages.map(toNavigationNode).toList
     val apiNodes = processApiPages(apiPages.toList)
-    staticPages ++
-      JList(new NavigationNode("API", apiPageDRI, ctx.displaySourceSets, apiNodes))
+    staticPages ++ List(NavigationNode("API", apiPageDRI, apiNodes))
 
   private def emptyNavigationJson =
       val strategy = new RenderingStrategy.Write("[]")
@@ -62,11 +57,11 @@ class NavigationCreator(using ctx: DocContext) extends PageTransformer:
     def defaultApiPages = processApiPages(input.getChildren.asScala.toList)
     val nodes = ctx.staticSiteContext.fold(defaultApiPages)(processStaticPages(input))
 
-    val navigationPage = new NavigationPage(new NavigationNode(
+    summon[DocContext].navigationNode = Some(NavigationNode(
       ctx.args.name,
       ctx.staticSiteContext.fold(topLevelDri)(_ => docsRootDRI),
-      ctx.displaySourceSets,
       nodes
     ))
-    val newChildren = input.getChildren ++ JList(emptyNavigationJson, navigationPage)
+
+    val newChildren = input.getChildren ++ JList(emptyNavigationJson)
     input.modified(input.getName, newChildren)
\ No newline at end of file
diff --git a/scala3doc/src/dotty/renderers/ScalaHtmlRenderer.scala b/scala3doc/src/dotty/renderers/ScalaHtmlRenderer.scala
index 5f7180a38af7..f64911e69912 100644
--- a/scala3doc/src/dotty/renderers/ScalaHtmlRenderer.scala
+++ b/scala3doc/src/dotty/renderers/ScalaHtmlRenderer.scala
@@ -29,6 +29,8 @@ import org.jsoup.Jsoup
 import java.nio.file.Paths
 
 class SignatureRenderer(pageContext: ContentPage, sourceSetRestriciton: JSet[DisplaySourceSet], locationProvider: LocationProvider):
+  val currentDri = pageContext.getDri.asScala.head
+
   def link(dri: DRI): Option[String] = Option(locationProvider.resolve(dri, sourceSetRestriciton, pageContext))
 
   def renderLink(name: String, dri: DRI, modifiers: AppliedAttr*) =
@@ -116,6 +118,29 @@ class ScalaHtmlRenderer(using ctx: DokkaContext) extends HtmlRenderer(ctx) {
     val renderer = SignatureRenderer(pageContext, sourceSets, getLocationProvider)
     (renderer, new MemberRenderer(renderer, buildWithKotlinx(_, pageContext, null)))
 
+  private def buildNavigation(r: SignatureRenderer)(rootNav: NavigationNode): AppliedTag =
+    val currentPageDri = r.currentDri
+
+    def renderNested(nav: NavigationNode): (Boolean, AppliedTag) =
+      val isSelected = nav.dri == currentPageDri
+      def linkHtml(exapnded: Boolean = false) =
+        val attrs = if (isSelected) Seq(cls := "selected expanded") else Nil
+        a(href := r.link(nav.dri).getOrElse("#"), attrs)(nav.name)
+
+      nav.nested match
+        case Nil => isSelected -> div(linkHtml())
+        case children =>
+          val nested = children.map(renderNested)
+          val expanded = nested.exists(_._1) | nav == rootNav
+          val attr = if expanded || isSelected then Seq(cls := "expanded") else Nil
+          (isSelected || expanded) -> div(attr)(
+            linkHtml(expanded),
+            span(),
+            nested.map(_._2)
+          )
+
+    renderNested(rootNav)._2
+
   private def buildDocumentableList(n: DocumentableList, pageContext: ContentPage, sourceSetRestriciton: JSet[DisplaySourceSet]) =
     def render(n: ContentNode) = raw(buildWithKotlinx(n, pageContext, null))
 
@@ -296,6 +321,8 @@ class ScalaHtmlRenderer(using ctx: DokkaContext) extends HtmlRenderer(ctx) {
         span(img(src := resolveRoot(page, s"project-logo/$fileName")))
       }.toSeq
 
+    val renderer = SignatureRenderer(page.asInstanceOf[ContentPage], sourceSets, getLocationProvider)
+
     html(
       head(
         meta(charset := "utf-8"),
@@ -319,7 +346,9 @@ class ScalaHtmlRenderer(using ctx: DokkaContext) extends HtmlRenderer(ctx) {
                 )
               ),
               div(id := "paneSearch"),
-              nav(id := "sideMenu"),
+              nav(id := "sideMenu2")(
+                summon[DocContext ].navigationNode.fold("No Navigation")(buildNavigation(renderer))
+              ),
             ),
             div(id := "main")(
               div (id := "leftToggler")(