If one accidentally with has taken over the .idea folder in its GIT versioning, is it unfortunately not possible via the IDE-PHPStorm, to remove this again.
You can run a command but just through the console, removed the folder from the GIT and locally further retains (No delete the painstakingly decorated settings!).
git rm --cached -r -f .idea/
After that, the folder should be entered in the .gitignore: