How do I set a keyboard shortcut to hold instead of toggle?

In Clip Studio Paint, I set the eraser tool to one of my pen buttons. When holding the button down, it would switch to the eraser, and when I let go it will switch back to whichever tool I was using before.
However when I set the eraser to the same button in Harmony, holding the button down will cause it to switch to the eraser and will stay on the eraser when I let go so I have to manually switch back to whichever tool I was using. Is there a way I can set the shortcut to hold instead of a toggle?

I don’t know if it is documented but (WIN/MAC) alt/option + key changes to that tool. Just holding the key toggles the tool, releasing it returns to the tool you were on.

eg. In your case to change to the easer (alt/option + e) or to stay on the tool your on and toggle to the easer just hold down (e). So you would just map the keyboard shortcut (e) on your pen button.