I agree that using 20+ sitemaps may seem a bit execssive,
I should point out that I very much subscribe to one of @rlkoshak's mantras: Home automation should just work without any (or at least significant) user involvment.
From this it follows that I really only have one (very limited) sitemap that I use on a regular basis. This gives me a sort of condensed overview of the system - some information points that I find important and take a look at on a regular basis.
All the rest of the sitemaps are there solely for maintenance/debugging purposes and thus are focused on providing as much details as possible for given parts of the system.
I have also choosen to have some sitemaps that focus on systems (or rather bindings), e.g. one for Z-Wave devices, one for network devices, one for DYI devices (interfaced through MQTT), etc.
... and other sitemaps that are focused on functionalitites, e.g. ligthing, security, presence, appliances, etc.
When it comes to navigating between them, I really don't. I have simply given them sensible names, and added them as favorites in my web browser,