I often want to move videos between playlists. I do zumba video and want to move videos from all videos playlist to cooldown or warmup playlist or retired playlist.
Sometimes I want to copy instead of move.
One approach that would work for me is when a video is playing and nothing is in the search results, put the video in the search result so when I change playlist I can add it to the playlist that I want.
A better still solution is a select box that allows you to choose destination, and icons in the playlist that let you copy/move to the selected destination.