In the process of setting up a new mac mini m4, I installed 2 browsers: firefox and brave because they both support vertical tabs and AutoScroll (which is when you hold down the middle button and scroll around the page-- I use an external mouse). AutoScroll worked perfectly on both until I installed BetterTouchTool and tried to setup 2 shortcuts for all apps: Cmd + Scroll Up -> Cmd + =, and Cmd + Scroll Down -> Cmd + -; which is to say holding command and scrolling with the mouse wheel increases / decreases the font size for many apps, particularly browsers.
After this change, AutoScroll in Brave still works fine, but AutoScroll in Firefox is messed up-- it usually just flashes the scroll icon when I hold down the middle button for a fraction of a second and then goes off (without me releasing the middle button), but sometimes the scroll icon will stay for a second or two and AutoScrolling does work in that brief time. I removed these 2 mappings, but it had no effect, then I removed BTT and restarted, but it also had no effect.
ChatGPT thinks BTT was responsible somehow, as do I (although i cannot prove it 100%):
→ This explains why Brave (which uses Chromium) still works: Chromium handles mouse input directly using raw input streams.
→ Firefox respects macOS' higher-level event streams more closely and is now receiving inconsistent signals for middle button "hold".
Is there a way I can be sure I have removed all vestiges of BTT so that nothing remains-- either any of its components, or any of the settings it may have changed during the install or mapping configuration?