Procedural generated nav mesh for city map

So currently working on a proejct with pretty sizeable city, and wanted to be able to identify different areas with custom costs (road / steep evironment would be very high cost and sidewalks/alleyways would be lowcost) procedurally, meaning without having to palce nav modifiers manually…

The city is made in Blender/Maya so any possibility of putting navmodifiers inside blueprints to buidl the cityy through Unreal is completly out of the way.

Maybe custom meshes for navmodifiers / identification through blender vertexcolor?
(how would i even apply these)

Any ideas?

Example of what i expect to achieve.

Image from Codewalk (Modding tool for GTA V):

bump bump