Thank you for your post.
At this time, only field names can be entered into the Sort Records by Field script step. Please enter this suggestion into our Feature Requests web form at: Company | FileMaker
Each entry into this web form populates a database file hosted by Product Management and Development. All entries are read, discussed and considered for possible implementation in a future release. Although I could easily copy your post and paste it into the web form, there are a couple of questions asked that only you can answer.
I made use of the Feature Requests page to document this suggestion. Thanks.