You can, but I find that if I have the tabs there, I use them or close them. I don't use bookmarks after I make them, so they just acrue. You're right I don't need 7000 open tabs, just like I don't need 7000 bookmarks. Part of the point of tab groups is you can more easily determine what tabs aren't relevant and get rid of them, so you don't wind up with thousands to start with.

If they're open as tabs, even in groups, I'm incentivised to close them when they're no longer relevant. For longer term notes I use a note-taking app that doesn't rely on my browser or computer staying the same. I don't like using a browser for that because it's just not a good tool for it.