Make staticmesh custom LOD coexist with LODGroup

The LOD Group is remove if we import a custom LOD for one of the generated LOD. This can be difficult when user change the LOD group setting later in the production, has the LODs that was regenerated are not regenerate with the new settings.

Import a static mesh

open staticmesh editor, set the LODGroup to Deco or any other LOD group

reimport one of the LOD created by the LOD group has a custom LOD (you can use the same fbx you use for the base static mesh LOD)

RESULT: The LOD Group is set back to none

EXPECTED: The LODGroup stay and the custom LOD is overriding the generated LOD