
Tab Mix Plus
Tab Mix Plus enhances Firefox's tab browsing capabilities. It includes such features as duplicating tabs, controlling tab focus, tab clicking options, undo closed tabs and windows, plus much more.
Always open new tabs to the right of the current one(which is not the same as setting browser.tabs.insertRelatedAfterCurrent to true).
Always open new tabs to the right of the current one(which is not the same as setting browser.tabs.insertRelatedAfterCurrent to true). You can however get the default behaviour by:
configuring the + button in the tab bar to not open tabs to the right of the current one(see addon preferences) using the ctrlaltt keyboard shortcut to open a new tab
firefox-extension new-tab-page tabs tweaking firefox-tab tab-addon tabs-tweak