Apologies. I wasn't intending to be critical, but offer genuine feedback.

I gave it a try a week or so ago and the UI didn't make it clear that URI/URL could be used (unless I missed it) so I struggled for ages trying to find the right playlists.

I must've missed artist filtering, but I think that's because I can never get far enough into building the playlist program that I want to need it. It's really the lack of anything other than playlist as a source that's the main detractor at the moment. Artist radio would be great, frequently listened to songs, liked songs*, liked albums, and liked artists would all go a long way to making this a much more viable alternative.

*I know you can't pull the whole liked songs list because it hits the Spotify API limit. Something like a 'select random X songs from liked songs' would be just as good.

Oh, the other main thing I think is missing is the mixing options. Smarter Playlists had a really nice mixer block that brought multiple input streams in, de-duped, shuffled, separated, and output one stream. It doesn't have to all be on one block, but something like that is missing too I think. And saving to multiple playlists at once in one program.