I found another way inside UE 5 :
Select your foliage
- Inside Tool > Merge Actors – merge it
It becomes separate fbx , BUT if you try to add it in scene, most probably it will be extremely heavy and your scene will freeze… and if you turn on Nanite on this fbx it will not help since Nanite struggles with small foliage (planes) type meshes.
- But to have it exported for another soft yes that would work fine.