How to revert to default theme DO11

Hi, I imported a new theme to try, and now it is impossible to revert back to the original one. No default.plt is available, as suggested on other previous posts. Any help will be appreciated. Regards!

See here for how to reset the things themes can change:

Thank you, I tried this option before asking for help, but I did not select the item that I wanted to reset... I assumed that this was like a full revert to original settings, but now I see that you can revert a single category instead. Regards!