not directly what was asked for but i think this should address the issue - i have added a field type to custom tags
- String (default)
these can be assigned in Preferences/ Layout/ Configure Fields and affect how the custom tag is filtered, sorted, and displayed
so assigning a custom tag to Rating means it will display a star rating. However i have made the assumption the rating is on a 0-100 scale as with other musicbee rating fields.
assigning a number type allows numeric sorting
its in the next update