This is purely cosmetic…In Tidal I have added icons to playlist names for certain moods etc. on the iPad you can type in icons in playlist names but they convert to dashes too.
(You May also note that I use hierarchical playlist names to emulate playlist folders, but that’s a different request!)
I think it’s down to the choice of characters used; not all render, so you’ll need to experiment. The following do render in iOS.
ϟ ★
I do see a couple but they are rough, black and white vs Tidal.
Again, I know this is a small cosmetic thing.
ϟ ★ 
