Multiple level bounds or level bounds Geometry editing

Is there any way to have multiple level bounds for one sub-level? And if not, is there a way to enable Geometry Editing for the level bounds?

I feel very limited by having only a single square box for the levels in our open world game. We’re dividing exterior levels into multiple sub-levels to ease the loading between levels, but having one big box makes this very hard to optimize.

If I were able to place multiple level bounds for a single level, I could optimize the loading/unloading of levels a lot better, and our game would perform better (the same goes for geometry editing a level bound).

Thanks.