Theoretically it should be possible to make child elements flow vertically instead of horizontally, by setting these properties on the parent: display: flex; flex-direction: column;. I tried that with a bunch of the tab elements and it didn’t work. The problem with addons like TST is that they glitch out sometimes, and you have to wait for the tabs to load, it takes much longer on my M1 Mac once I have 100s of tabs open (don’t judge me).
If you’re trying to modify the original tabs, my understanding is that you can’t which is why TST has to have both.
Take that with a grain of salt though, I just vaguely remember looking this up years ago when I started using TST.