*** UPDATE: This doesn’t appear to be working anymore, I’ll correct this post when I find an answer ***
I’ve found a lot of individuals have struggled with finding the way to build nav mesh on standalone level and have that stream in with their instanced levels. There’s not an obvious way to do this, but it’s actually quite easy.
The short version is this: Your global navigation mesh settings should be set to streaming static. Your persistent level’s recast navigation should be set to runtime streaming dynamic. Lastly, your desired level to instance and stream should be set to static.
I don’t know if this is meant to work this way, but it does. Essentially, the persistent level will try to rebuild nav when new geometry is introduced. However, when your sublevel’s already baked nav data shows up it just gets stitched in instead of a full rebuild.