If you have a playlist for an artist, with several hundred songs it would be useful to be able to use filtering functions to parse that playlist for further refinement. Also, you can’t even sort the items in the playlist, which would also be useful.
Another great feature would be to preshuffle the playlist and then save it as your play order. Yes, shuffle does exists as a playback item, but with expanding playback devices including Alexa, Siri, etc, sometimes getting them to understand the word “Shuffle” in a command request is difficult. Easier to give the at home “DJ” more creative options than to hope the device engineers can get speech recognition fixed.
While not a built-in feature, another user devised a way to create a smart playlist that automatically randomizes itself every time the playlist is opened/refreshed.
There is a request for searching/sorting playlists that I think covers your first paragraph.
It’s best to keep to a single request per thread. Makes it easier for people to vote on them.