`append and reuse` is chosen as default in DNA but this enumpropertyitem isn't added to the array when `Non data block packing` is disabled in Developer tools (see `rna_preference_asset_libray_import_method_itemf`). To fix this, change default in DNA to `ASSET_IMPORT_PACK`. In case of "non packing", change import_method inside `asset_library_add()` function. Also introduce `rna_preference_asset_libray_import_method_default` so that "reset to default value" operator works correctly. Pull Request: https://projects.blender.org/blender/blender/pulls/147104