Sorry Paul… I might be missing something… I should open Blender 4.3, append the brushes from the file, then duplicate any brush to get all of them into the saved folder?
When I append an older file with brushes they all show on the blend file (in the outliner), but nowhere else. If I try to use the asset shelf, nothing there. They do show, however, as materials that I can assign to the Grease Pencil objects. 🤔