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).
Sure, I’ll link it to you later when I get home. It’s really just a handful of lines of CSS.
But I suppose the main issue why you haven’t got flex-direction to work is because the scrollbox has
orient="horizontal"attribute and elements matching that are styled to have flex-direction horizontal in agent stylesheet with important tag. You cannot override that with userChrome. Practically this means that you cannot use standard flexbox display model for that scrollbox. Instead, I useddisplay: -webkit-boxwith its equivalent properties to make it vertical