Comment by brabel

IntelliJ lets you detach separate windows for almost all of the minor panes.

Click on the 3 dots on the top bar, View Mode, Window. It works for example for the file tree, Runners pane, Terminals etc. And it's easy to "dock" them again (an icon shows up in the window to do that) so you can try it easily.

I always keep some stuff like diffs, for example, in separate windows, it just makes me less confused about what's "temporary buffers" (as you would say in emacs) VS "actual files".