I’ve been wondering the same, sub-levels allowed for a modular workflow where you could isolate content and create it apart from everything else. Now you’re somewhat forced to create everything in one level.
Hey @MickyPain! Unfortunately the workflow for world partitions changed this significantly. However you can still have the same effect if you use the data layers for basically everything. That said, the lighting transfer is a bit more work, using level instancing should do the trick in this case, but the workflow is still a drastic shift. Level Instancing in Unreal Engine | Unreal Engine 5.0 Documentation