How should offer groups and product adding work in the admin form?
Search box inside each group. Typing "5600" instantly shows matching products in dropdown. Click "+ Add" to add without clearing search. Products list is drag-to-reorder. Groups themselves also draggable.
Groups collapse/expand. Split view: left side search results, right side current members. More spacious but takes more vertical space per group.
Both fix the search: uses LIKE '%5600%' substring match so partial terms work. Both support drag-to-reorder within groups and between groups.