The “Add Tools” UI is limited to icon buttons for now. To do anything more complex, you’ll need to dig into the JSON. Here’s the most recent documentation (which it looks you’ve found):
This is mostly still correct but we should do an updated version on the official docs site soon. In the meantime, the fastest path is to duplicate a tab (right click on the tab) and start tinkering with the resulting copy. Or you can find some community created tabs as a starting point: