Here is the solution a dev by the name of Iacopo shared with me:
- make the LOD level like you have been doing, with the automatic generator
- Find the LOD level (it is in a subfolder) Rename the generated LOD level to something else, remember the old name
- Make a copy of the actual level with the real foliage, name it to what the LOD level name was and put in same folder as the LOD level
- Open that new level, delete the landscape and other things you don’t need, but keep the foliage.
- Open the old LOD level you renamed, and copy and landscape static mesh, paste it into the new LOD level you made and position it correct (copy and pasting world position works)
Done! You will need to do this every time you tweak your foliage though…