Is there a way to play local files on iPhone from an already existing playlist?

[ChrystalShards]

Plan

Premium

Device

iPhone 7+

Operating System

iOS 13

My Question or Issue

Hello,

I added a couple local files to an already existing playlist. All the songs in the playlist are from Spotify but two. The two local files are playing fine in the playlist on the desktop version, but I am unable to find them on my iPhone. It shows the playlist is downloaded, but I am unable to find those songs in the playlist on my iPhone (keep in mind I am able to play them on desktop from the same playlist). I do know that to play local files on mobile you'll need to create a different playlist for those files and download them, but I'd like to have all my music, local files included, in one single playlist. Would that be possible? If so, please do let me know how, as it would really help me out.

Thanks.