Since Firefox 106, Firefox shows a "List all tabs" button in the tab bar no matter how many tabs you have open (even only one). You can move this button around the tab bar using the "Customize" feature, but you can't remove it. If you right-click on the button, then the "Remove from Toolbar" option is grayed out.
This page and this one suggests going to about:config, setting "browser.tabs.tabmanager.enabled" to "false", and then restarting Firefox to remove the button. But this isn't working for me. I've set the option to "false" and it's still set to "false" after restarting my whole computer, but the "List all tabs" button is still stuck in the tab bar.
How can I make this button go away when I only have a few tabs open? I'm running Ubuntu 2.04.1 LTS.