Hello friend,
You will need to open other instances to see the multiple levels, or add the levels on your world map and see one and other.
You can manage multiple levels to see them and compare on this way:
There’s a discussion about this here too:
https://forums.unrealengine.com/unreal-engine/feedback-for-epic/35464-feature-request-open-other-level-s-blueprints
I hope it helps.