Using mouse buttons in keyboard shortcuts?

I’d like to set up my shortcuts so pressing buttons on my pen with modifier buttons held selects commonly-used tools. But I don’t seem to be able to set mouse buttons as part of keyboard shortcuts. Is there a way to do this?

As you’ve found out, mouse buttons and mouse scroll wheel can’t be used in keyboard shortcuts.
The mouse buttons and scroll wheel, with modifier keys, are already heavily used in the Canvas Input Settings so anything you could think of, for selecting commonly used tools, is probably already in use.

The only workaround I can think of is to use your tablet settings utility to make the pen buttons give a keypress (if its possible) and combine that with Ctrl, Shift, Alt modifiers in the keyboard shortcuts.
However, that would remove the existing (and usual) ability of the pen buttons to do Pan/Zoom and the right-click for the popup palette.

Can you setup the ‘express keys’ on your tablet to do key presses for this?

I’m already using them heavily for other functionality, but I’ll see how I can rearrange my shortcuts.