There should be a feature that lets you search through your OWN playlists. Whether (some) your own playlists will show up in search is currently pure luck.
You could, for instance, expand the "Spotify:user:[username]" operator to be used as a normal search operator just like "track:[trackname]" and any other search operator.
That would, for an example let me search for "Christmas spotify:user:Marium0505" and have all playlists which include "Christmas" in the playlist name and that are made by me.
Of course, this search should only show public playlists when you're searching for another Spotify user, but both public and private playlists when you're searching for your own playlists.
Updated on 2019-03-09
Hello and thanks for the feedback!
A similar idea has also been suggested here:
Add your votes and comments there please! ;)
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