Document symbols broken (flat) from v1.9.25

[cristianoc]

From version 1.9.25 the symbols in the document appear as a flat list and not nested.

[cristianoc]

In 1.9.24:

In 1.9.25:

[cristianoc]

@aspeddro would you take a look?
I think it's after thing change: #629
Not sure how things are expected to be represented in order do communicate the nesting of elements.

[aspeddro]

I'm looking at this.

[cristianoc]

Turns out a bunch of extra work is required now: #655