It seems Elisa only supports m3u. I really wanted to use XSPF (see xspf dot org). It’s a libre XML playlist format made by the same people that created Vorbis, Opus, FLAC.
Sadly, it’s not so easy to find a player that supports it. VLC is one that does. Quod Libet too.
Even Amarok supports it, from what I read.
Hi! While I’m not a developer/maintainer of Elisa myself, this sounds like a reasonable feature to at least be considered 
KDE developers use a Bugzilla bugtracking system for feature requests - if this is one you’d like to see in Elisa, could you please submit it there as a “wishlist”-priority item? The community wiki guide to using the KDE instance of Bugzilla is here: Get Involved/Issue Reporting - KDE Community Wiki
I was going to use the bug tracker, but then I saw this note written in the description template:
If you’re not sure this is actually a bug, instead post about it at https:// discuss . kde . org
Ah - yeah, that’s basically there for when folks have a problem, and aren’t sure if something is a bug or if there’s a configuration change that could be changed to make it work.
Feature requests that are reasonable and generally line up with the intent of the application are definitely welcome