The Photos application question isn't really the point. What I need is to change the default save location in settings, and as I said in my original post the dropdowns don't open so I can't change them to This PC.
What happens is that when I go to save a file--any file, in any program--File Explorer presents me with OneDrive as the first option, so I have to scroll through the entire folder structure, which is long, to find the same file in ThisPC so I can save to my hard drive. This takes a surprising amount of time. If I'm in a rush, tired, distracted or whatever I inadvertently wind up saving to OneDrive. I assume that if I could change the default save locations, this wouldn't happen.