when it comes to tweaking the lightmaps and their size, UE4 is pretty much a nightmare.
I’d like to have an option to build lighting for one single actor/mesh. This way it’s faster to test the lightmap resolution of one single mesh.
The actors are affected by other actors and different lights, build the light for a single actor not sure if can be even possible (even if this is possible need to get the data from all the meshes in the path to get the traces and the bounces, so won’t be so fast as you think)
You can bake the AO in a 3D app
You can preview the size of the lightmap in the debug tools in realtime
There has been a request in for this for some time. It’s possible to do but would require some work to implement. With priorities focused on other rendering features this isn’t likely to happen in the near future.
Okay thanks for the feedback 
Taking into account only the lights without surrounding objects and rename it “Draft LightMap” or something like that would be an idea to “simplify” this feature 
The idea is to have the ability to
- Preview the lightmap result
- Tweak the lightmap resolution
- repeat
There’s more to it than that because you don’t necessarily know what the object affects or is affected by, it’s not just the lights that it is in the radius of.