When I close a file pane in TeXstudio, it seems to simply hide that pane and not fully close it. However, it's removed from the tree. When the file behind that pane is deleted externally, TeXstudio complains.
I understand that files are hidden instead of being closed for performance reasons. Is there a timeout or something like that after which they are forgotten? Also, I think it would help to see those files in the tree, perhaps under a special node "closed files", and also be able to finally close those files from there. Finally, is there a way to "refresh" a file, i.e. to completely reload all information TeXstudio might have computed about that file, from its contents on disk?