Is there a way to add an additional row of labels underneath a Matrix question?

Do you want to repeat the headers below the options or display new labels?
If you just want to repeat the headers, we have the option available on the survey builder page:
If a different label is desired, then you will have to use custom code.

I want to display new labels, do you have any idea where I can find a code for that?

Sorry I couldn't find any.