Looking for a specific song using the search function and then wanting that song to be played next seems like a fairly normal and common use case to me, but once again Music.app makes it seem like anything that’s not Apple Music was just left in there by accident. You can only right-click search results on the album art instead of the entire search result column, and neither “Play Next” nor “Play Later” are functional – consistently, also after restart and reboot. It works once you click “See All” in the upper right corner, but still only the album art is a right-click target in that view. Albums themselves can’t be right-clicked at all in search results, only opened by left clicking outside of the big play button they show on hovering (or the name). What a mess.