Levels are binary assets, which can lead to some challenges when collaborating with teammates working on the same area of the project.
However, by setting up Always Streaming sublevels, multiple people can work in the same game "space" at the same time. For instance, you might have a sublevel that contains all
the audio for your scene, as well as a sublevel that contains just the Static Meshes laying out your environment. Each sublevel can still only have one person working on it at a
time, but with careful segmenting of your scene's Actors, you can minimize overlapping work areas.
For example, ShooterGame has Always Streaming sublevels for audio, collisions, gameplay items, lights, and the surrounding vista environment that the player can see but not interact with.
You can toggle on Level Coloration to visualize what Actors in your scene live in which currently loaded level.
You can even have sublevels' Level Blueprints communicate with each other, so that allows a switch in one sublevel, for instance, to toggle a light in another.
In the Levels window, just right-click on any Level you want to have always loaded and hover over Change Streaming Method in the context menu. Then, click on Always Loaded.
If your Levels are going to be always visible in game, make sure they are all toggled on in the Levels window before rebuilding lighting or navigation.