Hey ,
Game Launcher is another method for packaging your game. It’s a part of Unreal Frontend.
option in Experimental section enables Game Launcher UI in Editor, which you can then access via Window > Unreal Frontend. It is normally only available in UFE, because it works for any project and not just currently loaded project, and this can be confusing to new users. That’s why it’s currently in Experimental section. If someone wants it available in Editor, they can turn it on with that checkbox, but it’s not enabled by default because conceptually it doesn’t quite fit. Generally recommended approach for launching games from editor is PIE or Launch in toolbar.
What you’re looking for is something developers are looking into and may eventually provide as part of Unreal Launcher. overlapping terminology can be confusing so all of these may go by different names or may not be available in future.
Hope that clears things up!