Select with custom values?

Hi, why don't you just register all values when defining the field? What is your case when you need to fill the advanced select with custom values?

PS: I will add a search box to the forum 🙂 Thanks for the idea.

I think it's possible to get gravity forms when register meta boxes. The hook rwmb_meta_boxes fires at admin_init and at that time everything is ready. You can use $wpdb to query the database to get the data you need and put it in the options parameter.