Is this what you mean:
The structure of the user library folder regarding fixture types and fixture type resources changed. Fixture types are
now located in gma3_library/fixturetypes. It is no longer distinguished between grandMA3 fixture types and GDTF fixture
The additional new folder "fixturetyperesources" with its two subfolders called "gobos" and "meshes" is now the location
for gobos and meshes. Copy your custom gobos and meshes into these subfolders to be able to import them to your
show. Exported gobos and meshes are also located there.
can you please elaborate on where the old meshes are?