Solid part 2- about preset creation, thank You.
Part1 is missing key part- thumbnails generation.
Plus You have all Your models in one scene- that`s convenient in illustrated case- relatively light grass objects.
More real world case is tress library, easily exceeding gigabytes in size- I wouldn't dare to put all those trees in one file.
My workflow is:
Use
hcg asset browser for thumbnail generation- one max file,- one thumbnail.
Then from folder like this:

make library like this:

using script I wrote-

it`s not too user friendly and still have some UI issues, so cant really share it for now..
but iToo team could easily write similar and better during lunch break...
P.S. Can I please ask You custom background color for library browser? I want white, please...