EDIT: With 10.0.7, please do NOT use the Theme Switcher app at this point, it has been reported that it does not work with 10.0.7. Wait for the developer’s instructions.
There is now a handy app for theme switching!
Go here to download it: http://lts.coldpressgroup.com/#
As always, first make a back-up and read the instructions.
Please note that the themes folder that the app uses and the app itself must locate on the same drive.
The app done by GearSlutz forum member birk. Cheers!
Ps. Why did I not try this earlier? This is brilliant.