When I make new level file by "Save Current As", new level file take all levels in same folder as sublevel

Check this:

As you see, New level made by “Save current as”, takes all levels in same folder as sublevel, automatically.
I can not remove those sublevels.
In PIE, because all actors in those levels, play is almost impossible. Editor is freezed soon, or crash.

If I duplicate level file, samething happens.

Anyone saw similar like this?