I’ve found another workaround that may suit your needs. Nav grid generation is messed up for Creative Props but it works for Static Meshes. You can attach Static Mesh that will serve a role of custom navigation collision to your Creative Prop. This way Prop will drive movement and Mesh will drive Nav mesh gen. Just remember to:
- set Static Mesh Component within Static Mesh to “Movable”
- set Static Mesh property “Can Ever Affect Navigation” to TRUE
- set Static Mesh as “Hidden in Game”