I don't use submodules, but I do use git repositories inside other git repositories, and let IntelliJ manage them both simultaneously as if they were two differ

I don't use submodules, but I do use git repositories inside other git repositories, and let IntelliJ manage them both simultaneously as if they were two different projects. Works fine. I once enabled it as submodule to test. It adds nothing and from that moment any change in the child creates a change in the parent, which for my use case is totally unnecessary (I want both of them to be independent, even if hierarchically one is inside the other). Submodules are probably a good option to have libraries that you rarely touch, so you can update/modify them as with a maven/gradle project. For most other user cases submodules make more problems that advantages.