[FEATURE] Add "Expand all" & "Collapse all" for navigation item panel

[IceAsteroid]

Is your feature request related to a problem? Please describe.

It's difficult to navigate through the navigation panel when headings are too many as long as the note becomes large.

Since, all headings of different levels are expanded by default.

I'd like to scroll through all the first level headings to have an overall picture of how the note is organized after long time no visit. Instead of using the "Find navigation item" right in the navigation panel.

Describe the solution you'd like

Add a mini menu by right clicking in the navigation panel or by a shortcut to have two options "Expand all" and "Collapse all" for expanding or collapsing all levels of headings.

When clicking on a heading that has sub-headings, its sub-headings should remain collapsed.

Any ideas?

[pbek]

I think it's the same problem as here: https://github.com/pbek/QOwnNotes/issues/1978#issuecomment-743042167

The largest problem is that the navigation panel is regenerated all the time while you are typing and it would be very hard to track and restore what was open and what wasn't, because there is no clear reference to a headline. It's just text.

[IceAsteroid]

@pbek Maybe look at how ZimWiki has achieved this in its code? ZimWiki has the exactly feature that I described..

The reason I try to use QOwnNotes is because it supports Vim keybindings to edit notes, fantastic, while other simple yet usable note-taking programs don't support this.