I played yesterday with integrating better navigation for mobile devices.
In the video is my current test theme default-bootstrap (not yet migrated onto TB).
If one is willing to fully integrate something like that into default community theme,
I could share the working source of it, which is based on w3css stylesheet parts.
It does not work with swipe gestures as it only uses toggle buttons, so no external
script is needed, just few inside script lines.
This was the base of my current design:
https://www.w3schools.com/code/tryit.asp?filename=FSS50OW16PT7
Video
https://youtu.be/tdv_KVPBxOc