Didn’t find my ideas here: suggest-feature-collection-t1482.html
So here we go:
- crossfader 0…15sec
- gapless playback - on/off
- replay gain - track/album/auto
- autoplay/resume after start - on/off - [https://github.com/volumio/volumio-plugins/blob/master/plugins/miscellanea/auto_play/auto_play.zip]
- upnp renderer/airplay/shairport - on/off (one switch for each)
- hdmi - on/off
- expand sd-card/ssd storage
- restart volumio ui or restart mpd button
- UI password option
- update library from folder menu (play, add to queue, clear and play, add to playlist, update folder)
More thoughts:
a) random/repeat/gapless/crossfade should be easy to access from the player status or below the circle. (Does someone use playback - “go to” - tweet track? The fewer clicks the better.)
b) or even worse with sources: browse (1) - music library (2) - NAS/USB (3) - Alias (4) - path (5) - file (6) …Clearly too much clics…
- Solution: Browse (1) - music library/radio/usb/alias (2) - path (3)
c) player artist/title layout:
ARTIST (most important H1)
TITLE (also important H2)
ALBUM (not so important H3)
d) technical status/info for geeks 
- input file info - already in the status circle
- output file info - playing file
- connected dac/hat info
- cpu/ram/temperature
Don’t get me wrong, volumio is great, especially UI, but could be even better!
edit: autostart/resume plugin link. This should be in plugins management!