How to Make a Copy of Windows 10 Default?

Hi, I'm brand new to WindowBlinds. If possible, I'd like to create my own dark skin for Windows 10, but I want to start with the Windows 10 default theme. Is there any way to make a copy of it to use as a starting point? (I know I can't edit the default.)

I haven't found any theme I'd want to use as a starting point for creating my own dark theme. I like the Windows 10 default theme, I just want to change the backgrounds of folders to dark grey and a few other tweaks.

Thanks for any help!