There's no rule. The only rule is to be consistent. If you want to capitalize the first letter of each word--then do that. If you only want to capitalize the first letter of the text, then do that. There's no "best" way to do it. Just be consistent with your styles.

Thank you so much!

Hello, I have a simple question.

When designing computer systems, is there any rule about capitalization of names of tabs or buttons?

For example, do I always have to write "User Setting" or "User setting" is also acceptable?

Thank you in advance.