The playlists tell you in the bottom-right corner how many tracks there are, what the total play time of all tracks is as well as the total space required.
If you are selecting several songs from the collection, the same info will be displayed.
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I created a playlist called "All"
I copy in to it all tracks from each playlist, making sure I don't copy duplicates.
This tells me how much storage I need and how many tracks I have across all playlists. I never exceed 1000 tracks.
I find I use the All playlist a lot when looking to mix things up.
Another thing I do is copy the tracks across first then the playlists.
A few times I've found playlists with missing tracks, this has never happened since copying the music over first.
