HOW TO ENABLE THEMES IN ROBLOX STUDIO
STEP 1: Make sure ALL ROBLOX Studio windows are closed.
STEP 2: Where ever your ROBLOX Studio is placed (likely on your desktop), right click it and click Open File Location.
STEP 3: Find this file in your ROBLOX Studio Folder:
STEP 4: Right click that file, and click Edit.(Notepad++ is recommended for this step as Notepad/Wordpad is not optimal for XML editing.)
STEP 5: Hold down CTRL and F.
STEP 6: Type in “themeoptions” in the box, and click Find Next. (The look may be different on other versions of Windows like 7 / 8 or 8.1 / 10.)
STEP 7: Close the Find window and look for this:
STEP 8: Set the circled text to true.
STEP 9: Click FILE.
STEP 10: Click SAVE. NOT SAVE AS. (or hold down CTRL+S on your keyboard to save)
STEP 11: Close the window, and you are finished!
(i am open to all comments)