How to add a sort criteria for custom (non-alphabetic) order on a list Field

I would like to add a sort criteria to sort in a custom (non-alphabetic) order on a Field of type 'List (text)', and have the order modifiable in the future.
Currently, when I add a sort criteria on this Field, I get the options 'Sort ascending' and 'Sort descending', but I'd like to specify a custom sort order instead.
Is there a way to do this?