Generator filter: exclude if present on named playlist

[da2x]

Is there a way to exclude songs from one playlist songs that are present on another playlist? Something like sx"Christmas" (source exclude songs on the named playlist Christmas). I don’t see anything obvious on the generators wiki.

The use case is to generate a top songs list from all sources that excludes the Christmas playlist pests.

[Taiko2k]

There wasn't, but I've now committed this feature. The new code is px, so, px"christmas". (Its a filter, not a 'selector', so goes after the 'a')