The LOD selected to be edited should be saved correctly, allowing different remesh results to be saved as different LODs of the same mesh, _i.e. remesh with 1 cm triangle size as LOD0, 2 cm triangle size as LOD1, 3 cm triangle size for LOD2, etc._
This is necessary for making uniform-topolgy proxies that maintain their uniformity throughout a LOD chain; Auto-generated LODs created by automatic reduction do NOT retain uniform topology and are therefore unacceptable for this purpose. Uniform-topology proxies are used for overlay effects relying on WPO whereby a normal mesh's vertices would deform unevenly or break apart."
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-183213 in the post.