Is it possible to add hotkey for just holding both right and left click at the same time? In some applications this is used for panning or zoom
I dont think that is the same thing. What I mean is that when you hold left and right mouse click down panning would happen.
May you show some example of what you mean?
Here is example from Unreal engine asset editor:
I dont know how to setup screencast for it but here is an example:
left click = pan horizontal
right click = orbit
left + right click = pan vertical
I wonder if its possible to trigger hotkeys by left + right click combo in Blender too
No. There is no Left & right click together option in the Keymap settings.
Go look…
Edit Menu > Preferences > Keymap.
Type Pan in the search box at top right. Scroll down to the 3D view section (Press enter or click to finish the Pan text entry if you cannot scroll).
Expand one of the Pan view entries
Click the Mouse/Trackpad/Pan Menu and look at the options… There is no left and right click.
Use the default Shift-MMB. Or perhaps try changing to Left Button and change Any to Click-Drag or Double click.
If you change something a Restore Button will appear - so you will able to find it again if you want to undo your change.
In this case, Autohotkey should be able to handle it.