Right now when you paint foliage and you switch between multiple areas of different foliage types, there’s a lot of work having to reassign the meshes and their settings. Most of the time you just forget what you used before and try to compromise until it looks okay enough.
I know the older Crysis (or was it FarCry?) editors had this feature where you could define different sets, and changing a set changed the instances in the world too. You could switch between these sets at will.
This was really useful and increased productivity for outdoor scenes a lot.