But it's still possible to have a studio listed, and click to leave it, and not be able to click to rejoin it. That's on purpose: it happens when you don't curate the studio, but your project is in it.
When that's the case, we need to visually communicate to the user that the studio can't be joined; perhaps by displaying it with a muted gray color.
https://github.com/LLK/scratch-www/pull/2682 made the add to studio list only show studios whose membership status you have the power to change.
But it's still possible to have a studio listed, and click to leave it, and not be able to click to rejoin it. That's on purpose: it happens when you don't curate the studio, but your project is in it.
When that's the case, we need to visually communicate to the user that the studio can't be joined; perhaps by displaying it with a muted gray color.