Disabling Thunderbird single character shortcuts with BTT

Been using BTT for about 5 years, have a few simple keyboard modifiers and scripts set up but nothing much. I'm convinced I haven't even scratched the surface of what BTT can do.

When running Thunderbird, I used to have an add-on that would let me disable single character keyboard shortcuts like A, K and W. With the newest version that add-on no longer works. There are no other menu add-ons that work with this newest version.

I figured I could use BTT to re-assign A,K and W to nothing or an innocuous keystroke. Indeed possible, but the problem is that the BTT re-assignment ALSO works in actual message windows (that open separately from the main TB window) and typing a message without A, K and W is a bit problematic. Both windows seem to be called "Thunderbird"...

Does anyone know if there is a way to somehow differentiate between the main Inbox window and a "child" window for an actual message using BTT?