Managing themes in Keynote (9.2.1)

Thanks. I'm not sure if restarting and then right clicking made it work this time, but at least reading this solution made me try again. I have to point out, however, I remember when using a Mac was intuitive...but now if you want to DELETE a theme, you have to first go to SAVE theme (not what I want to do...but wait, there's more!), then click on ADD THEME TO CHOOSER (not what I want to do...but wait, there's still more!), which then adds a theme that I'll then need to delete by right clicking, and then I can finally get to the business I need to do. I really, really, miss the Apple of 20+ years ago. And I really, really, want to thank Gary! Cheers!