Unreal Engine supports runtime navigation generation. However, a flag needs to be set in the projects setting.
Edit > Project Settings > Navgation Mesh > Runtime > Dynamic
This will automatically regenerate the navigation on runtime generated dungeons. Be sure to have a
Nav Mesh bounds Volume large enough to wrap the whole dungeon. There is an example in the quick start guide to automatically wrap the navigation volume around a dungeon after it has been built.
If you want to use runtime navigation with a builder that supports level streaming (like
SnapGridFlow), enable the following flag in the dungeon actor