Since the reddit community is now private, I want to ask this question again here :) The encoders intrigue me but I just lack the imagination to figure out how to use them for anything else but volume control..
Manual layer switching. Though I think there are some GitHub projects which add active application detection to qmk, I just haven't gotten around to it yet.
I have one set to tab on clockwise and shift+tab on anticlockwise, allowing to you hold alt, shift, ctrl or gui while turning it to determine the function. It's also great for code indentation.
As for the inwards click function, I set that to caps lock as it's not used frequently but nice to have when needed
Volume knob with a quick push for muting is always a classic. If I’m on a set up with two knobs, I also like including next track, previous track, and pause/play as the secondary knob.
It’s a matter of taste, I use the encoder when I need to go quickly into a given position, without any requirement for the precision.
So it’s ok for me to use it to scroll a webpage, zoom-in zoom-out inside a picture, or set the volume, but I prefer using a real key if I need to switch between tabs or applications.
Personally I have mine set to switch windows mostly, but lately I've preferred using a set of custom keycodes on a nav layer for that. I have to hold down a key to activate the layer. Tapping one key sends tab, the other shift-tab, and both hold down alt if it isn't held down, starting the window switcher. Releasing the layer key releases alt, implicitly selecting the current window. It's faster for me to do this than to move my hand to the knob.
I have a pimoroni trackball that I use for a variety of things which might feel good on some knobs too. I think that text cursor will likely feel pretty good, particularly if your encoder ticks while twisting. Then you could make one tick equal one arrow key press, and you dial in precise cursor location.