This automatic transfer-weight from object to Grease Pencil (Lineart) , is a feature from Goo Engine.
But, you can replicate this in Blender 4.5 using Geomtry nodes.
This setup consist in transfer and store a Attribute with same name based on surface proximity, i imagine that Goo Engine use same approach but on "backstage"
Make it reusable:
Expose as inputs the Object and Name of vertex group, this make possible that you use same Geometry nodes setup in others GP objects.
For use with Collection
Switch your Object info node for Collection Info node, and add a Realize Instances node beetween this and Sample Nearest Surface.



