Can you PLEASE fix the FBX export "InstaLOD -> Merge material" and add a custom alternative for custom merge variation.
[X] Advanced Material Merge
List all meshes/sub meshes in a table, in the second column you write the merge name, all meshes with the same "merge name" get merged, pass info to InstaLOD, simple as that...;-)...
________________________________ Mesh Name | Merge Name ________________________________