I know where you want to see it. But, creating a dummy spouse and dummy marriage is going to cause you problems elsewhere. No entry in RM is in a vacumn and only affects the screen you are on.
You could take Renee's suggestion and enter [Never married] or [Single] in the suffix of the person's name. Then it will show and print where ever the name prints. For Narrarive report sentences, you might want to change default sentences to read [Person:Given:Surname] so the suffix doesn't print.
Renee's other suggestion was to enter it into the Referennce number fact.
If you go to Tools, File options and choose Reference number (REFN) from the dropdown Number to display after name menu, whatever is entered into the Reference number fact description box is shown on screens and printed in reports instead of the person's record number.
This will show never married or single to the right of the person's name in the place of the person's record number.
If you don't want the fact printed in reports for a person, you can mark the fact as Private on the Edit person screen or Timeline view.
Or, you could customize that fact's sentence for that person on the Edit person screen to print [Person] was [Desc]. and enter never married or single in the description for the sentence that prints in a Narrative report.
To create a user defined fact, go to lists, Fact type list and choose Design new fact.