This feature could easily be upstream to i3. This could be added as new option to the focus command, such as focus last. Example usage would be:
bindsym $mod+Tab focus last
(This is just an idea, and is likely not be possible to implement with i3's current mark binding system)
I believe it would be possible to store the history of focus to allow using the i3-back switch command multiple times in a row,
which would match how Alt+Tab works on other desktop environments.
Considerations:
- It would be nice to know when
$modis released, which would reset the history index. This limitation makes it likely not possible. Alternatively, use a delay.