Ah, I was looking into the LOD option first, but I wasn’t able to get it working. I tried exporting my cubegrid mesh as an fbx and reimporting it as a LOD but that just resulted in the mesh vanishing.
Update: tried it again, and it worked this time, except the mesh comes back distorted
Here you can see the original mesh on the right, and the reimported one on the left.
I must have some weird setting active or something.