The multi form goal block currently only loads 10 forms and the search box will only search within those 10 forms on the list. There's no way to select or find a form outside of the list.

The workaround, for now, is to use the [give_multi_form_goal] shortcode instead: https://givewp.com/documentation/core/shortcodes/givewp-multi-form-goal-shortcode/