Change navigation item to a button

Hello. I am trying to change the last item in my navigation menu into a button, in a custom made header using Beaver Themer.

I am using WP 5.5.1 + theme Astra Pro, in case that is of help.

I came across this page in BB’s documentation, but it did not work, I assume because it was written for BB Theme rather than Themer.

I’d be grateful for any help. Thank you.