You can only pin a tab to place this tab at the far left with only its icon showing, for a bookmark you need to open the bookmark in a tab. *https://support.mozilla.org/en-US/kb/pinned-tabs-keep-favorite-websites-open You can search the Add-ons website for a suitable tab group extension. Note that you can customize the Firefox View button and place it on any toolbar. *https://support.mozilla.org/en-US/kb/customize-firefox-controls-buttons-and-toolbars