I found some issue with the suggested code: container-type triggers containment, which in turns can cause layering issues. The original selector .txp-layout-4col-3span also applies to the wrapper around the search box. the containment cause the dropdown to layer below elements / blocks later in the page.

A possibly better selector can be #main_content. I’ve updated the demo sample code.

–^–

PS - Eventually it might an interesting idea to add a class to all those larger content edit columns.