Hey, while it would be easy to modify the NavMesh path-finding to take jumping height into account, it is a whole different beast to actually tell the AI when to jump and when not to. A simple bool wont work for a few reasons.
Unreals system basically uses NavMesh and NavLinkProxies to allow you to implement this stuff. You could use EQS to scan the level around you and place NavLinkProxies dynamically. You could check the Engine/Source/Runtime/AIModule and Engine/Source/Runtime/Navmesh for all the additional classes involved in this.
For open worlds or at least big worlds like yours, I think the best solution would be to implement your own path-finding. One thing that could work is a sparse voxel octree instead of a NavMesh. You could check if the neighbouring voxel is reachable, if it is below or above the current location and if is safe to drop or close enough to jump up.