The Epic Games Launcher can be quit without any issues by right clicking it and selecting quit in the Dock.
The UnrealEditor however stays open, it doesn’t react to that, I have to go to the ActivityMonitor and force quit.
So when opening one project, closing that then opening another project and closing it, I have two UnrealEditors open, when opening and closing a third project it simply adds to that.
It doesn’t even look like that the Editor is crashing (I think I only got once or twice a crash report window), most of the time there is no crash report window, so I guess the editors didn’t crash.