Feature request: improve documentation navigation (and css?)

[DocSunset]

There are no breadcrumbs, no side panel/tree view, no top navigation bar, etc.; the complete lack of page-wide cross-document navigation makes it very frustrating to move between pages (particularly the high-level API docs and low-level API docs which seem to contain most of the relevant documentation). I can bring the usual top bar back by changing DISABLE_INDEX in reference.doxygen to NO, and the side panel can be reinstated by setting GENERATE_TREEVIEW = YES. Then I see that doxygen "helpfully" generates a bunch of other documentation pages that I'm guessing are the reason why these navigation features were suppressed in the first place? I suppose that it was decided that giving access to the automatically generated data structures and files documentation subtrees would muddy the documentary waters, and so the navigation was turned off? If that's the case, perhaps some modification could be made to the default header HTML to add navigation links between the main documentation pages?

For what it's worth (~ $0.02) I would also appreciate if the documentation was nicer to look at. I have recently used this plugin on my project and it seems pretty nice overall, but I have only had it running for a couple days so I can't 100% endorse it so soon. I can say, at least, that it's easy to set up and looks good so far.