Sidebar Tabs for Firefox 12.0.5

Sidebar Tabs for Firefox emulates sidebar tabs displaying them vertically.

You can also manage your tabs by grouping or expanding them. Sidebar Tabs uses some experimental Firefox features; if you plan on using it, you will need to activate them in # about:config

Set svg.context-properties.content.enabled to true.

# Tab group

Select tabs by "Shift + left click" or "Ctrl + left click" ("Cmd + left click" on Mac) on each tab.
Drag one of the selected tabs with "Shift + left click" and drop it on the tab you want to group.
You can also group tabs by selecting "Tab Group" from the context menu and selecting "Group Selected Tabs."
Tab groups are color-coded for each.
Collapse/expand tab groups can be done by clicking the colored part or from the context menu.
The new tab opened from the tab in the tab group will be displayed as the tab of that group.
To cancel the grouping of tabs, you can do it from the context menu.
Tab groups will not be saved during private browsing.

Sidebar Tabs is another option to utilize tabs in a different location providing a different look to your browsing session along with some additional useful features.

Similar:
Restore Accidentally Closed Browser Tabs
How-to Mute Tabs in Google Chrome, Mozilla Firefox, and Microsoft Edge
How to Restore the Close All Tabs Warning in Microsoft Edge
How to Make Google Chrome and Mozilla Firefox Run Like New Again

Sidebar Tabs for Firefox 12.0.5