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.
