TabToggle от Sriram

This addon is meant to help toggling between 2 active tabs back and forth with a click/keyboard shortcut

Highlight 2 active tabs (of the same window) by clicking on them. The addon keeps tracks of the last 2 active tabs dynamically.

Clicking on the Toggle button (or Alt+Q shortcut) toggles the active tab.

The addon is just a naive port of the legacy addon with the same functionality (by firesofmay)