Adding a Search Modal to Primary Menu

I’ve read through the documentation at https://docs.generatepress.com/article/navigation-search-modal/ and through past support topics, and I still don’t understand how to add a search modal when using a navigation element.

1. I checked the check box in Customizer > Layout > Primary Navigation.
2. I made a block element and chose type Search Modal. It is applied to the whole site.
3. The documentation says to add ‘ data-gpmodal-trigger=”gp-search” ‘ as a custom attribute, but I don’t see where to add a custom attribute.
4. No modal shows up.

All I want is a magnifying glass at the right of my menu that triggers a search box to pop up. I was easily able to do this in GP 1 using the built-in Primary Navigation.

Also, it looks like I’m supposed to add a magnifying glass icon manually. But I don’t see any such icon among the built-in icons. Is everyone getting one with SVG?

I understand that I can set the settings for the modal in the Customizer, so I think once I have it appearing at all I’ll be able to make it look right.