Hi UHK community.
I’m really happy with UHK v2 and the only question I have so far is: I don’t have left button cluster, I use only trackpoint. I’m used to using it with my index finger, but I want to try using it with my thumb. The only thing is that I won’t be able to click left mouse button in the process.
So the question is: can I automatically toggle another layer if I use trackpoint?
Well, discrete navigation modes (e.g., caret or media) can be remapped to macros. So yes, just create a macro to toggle the layer, remap all directions of one of those navigation modes and configure navigation modes per layers… You will also need to map a macro to untoggle layer somewhere in the toggled layer, and you will have to unlock the layer manually. See the smart macro reference in Agent, or the reference manual at https://github.com/UltimateHackingKeyboard/firmware/blob/master/doc-dev/reference-manual.md.
I just mapped the left case button as left mouse button. So I can click using my left hand (thumb).
Same here. I do have the left module, but found that I do not really use it much and actually prefer the left mouse click on the left case button, most of the time. So this is surely worth a try. 
If you’re on Windows you can turn on ClickLock, for one thumb functionality. There’s apps for other OS’s.