Is there a way to select all unused text styles and then delete them all in one shot?
Here is a screenshot showing that I have created all these text styles, but I have not used all of them in my design, so I want to delete the unused text styles at once.
For each text style you have (in your case, 14), you can select the text layer, then apply “Select all with same text properties”. This will confirm for you whether or not that style is being used elsewhere on the same page. If not, you can safely delete the unused text style. Unfortunately, this doesn’t work across pages.