Hi There,
I think you’re looking for the Hide During Breakpoints option which can show/hide an element base on the screen size.
If so, it is under the Customize tab. If not, please clarify.
If you have not watch yet or even if you do already seen it, I advice to watch it again the videos created by The Great Kory (X & Pro lead programmer) on link below regarding the Flexbox and Navigation. You might not need the Hide During Breakpoints option if you can utilize the Flexbox properly.
https://theme.co/apex/forum/t/pro-tips-and-tricks/214
On other note; please do not refer the Theme as X Pro because that is two different product. X is the classic theme, and PRO is the one with the Header and Footer builder.
Cheers!