SortSelectedTabs by DeKay

Sort Selected Tabs does exactly what it says - no extras, no bloat.
Simply select multiple tabs in Firefox, right-click, and choose "Sort Selected Tabs (A–Z)" to arrange them alphabetically by title.

Unlike other tab managers that often sort all your tabs or don’t work as expected, this add-on only affects the tabs you’ve selected - nothing more, nothing less.

• Works in normal, private, and container tabs.
• Keeps tabs in their original groups and containers