Hi, is it this one? https://addons.mozilla.org/firefox/addon/max-tabs-web-ext/ I think it should have a toolbar button, but if it's grayed, maybe not. Does the gear button allow pinning it to the toolbar? There isn't a direct connection between tabs and processes. Some processes are global to Firefox. You can see which processes are used for which parts of Firefox by opening the built-in Task Manager: Shift+Esc or type/paste '''about:processes''' in the address bar and press Enter to open that list.