I spent 15 minute to understand what the extension was really doing. Actually, it goes to the last active tab when clicking again on the active selected tab. This work as expected.
For the moment I don't know what this can be used for... Could you please give some use cases in the description?

Edit: you're right, the ability to switch between two tabs that are not close is actually very useful! Nice idea!

Seems to work. Thanks!

Adds extra functionality to Tree Style Tab without any drawbacks that I can find. The keyboard shortcut is also quite useful, makes it easier to multitask in some cases.