The add-on works well. There is one pretty annoying problem with the tracking button in GitLab (and maybe other tools too): The focus when using keyboard tab isn't visible enough and also scrolls the page instead of interacting only inside the tracking button popover. Also the drop downs for selecting the projects or tags don't correctly work with the mouse. Clicking on the drop down once, closes it immediately. So currently, I have to open the drop downs via keyboard.

Update: After the latest updates, the focus handling got much better.