Works well (after turning on "Run on sites with restrictions").

Deduction for:

1. not providing a link to the source code. The source code inside the .xpi file is not obfuscated though, and does not contain any funny business
2. Not possible to disable keybind (I have not interest in the merge tabs action)
3. It does have some unnecessary features (go to tab binding)
4. The attach tab action is not very helpful

Works well if you have one primary window and work out of that. The detach works, but merge and attach seem to pick a target window at random.