This may or may not help. This is how you set default blueprint properties. You have to get the default class
ut_asset = “/Game/Brushes/CustomBrushes/test_brush”
unreal.EditorAssetLibrary.duplicate_asset(in_asset, out_asset)
get the generated class
blueprint_generated = unreal.EditorAssetLibrary.load_blueprint_class(out_asset)
from that, get the class default object ( the actual template for the blueprint )
blueprint_class_default = unreal.get_default_object(blueprint_generated)
set or get properties
blueprint_class_default.set_editor_property(“Name”, “Testy”)
unreal.EditorAssetLibrary.save_asset(out_asset)