Using Theme The Box PLUS, client wants Search Bar to appear on main page instead of on Sidebar. I’m trying the advice here How to Add Search Bar and they suggest using Screen Options/Advanced Menu Properties/CSS Classes.

This is not available on my localhost instance, which is using WP 5.7.2 with theme: The Box

Question: Does WP determine what appears on Screen Options or are Screen Options Theme dependent?

If its part of WP and not the theme how do I enable Screen Options/Advanced Menu Properties/CSS Classes ?