Odd behavior with new Firefox vertical tabs

Bugs or Unexpected Behavior
1

I have an action configured for all apps to send command-W on tip-tap middle with my magic trackpad. I typically use it to close browser tabs.

I recently upgraded Firefox and the latest version offers a new feature to have tabs displayed vertically down the right edge of the screen instead of across the top.

Since applying the Firefox upgrade, the action doesn't work correctly. It now makes the "top" browser tab (in the vertical list) the active window and doesn't close the window I was in when I performed the action.

It still works correctly in Safari, so I think it's pretty certain that something in the Firefox update isn't working correctly with BTT.

Machine info: Intel Macbook Pro
OS version: Ventura 13.7.4
Browser Version: Firefox 137.0.1
BTT version: 5.304
Affected input device: Magic Trackpad.

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Additional information (e.g. crash logs, related issues, etc.):

2

I've just tested this and it is working on my end. However the versions are different on my end:

macOS: 15.4 (24E248)
Firefox: 137.0 (aarch64)
BTT: Version: 5.294 (2025033105)

Do you see it in "Recently Used"?

3

Yes, I do see it in "Recently Used", and that sort of solved the mystery.
What I saw there was a Firefox-specific action to send option-command-right arrow for the TipTap Middle. The remaining mystery is how that got there becuase I swear I've been using that action regularly for a while to close tabs in Firefox.

Either way, I've deleted it now and it works as expected. Thanks!