I’m trying to change the appearance of the header so when a user is logged, he or she sees their username currently, but I’d rather they see their first or full name in that area, if they filled that out.
I went to HivePress/Settings/Users/Display to change to full name from the pulldown, but I still see the username in the header instead.
It is possible but requires overriding file /hivepress/templates/user/login/user-login-link.php via a child theme. If you’re familiar with the theme customization basics please check this tutorial Customizing Templates I HivePress Developer Docs - YouTube
Please try changing get_username() with get_full_name() if you already copied this template part to a child theme. The name fields are not guaranteed to be non-empty unless you added them to the registration form, you can also try using get_display_name() instead