OK, so something like moving playlist files should be a low priority, even if you had hundreds of them the total amount of disk space involved is only going to a few MBs or so. It's things like music files, photo files, and especially video files that will all add up to be using storage space. If you need to free up storage space focus your time and efforts on moving files that actually result in a practical freeing up of storage space. Worrying about little text files isn't productive in the short term nor the long term. Use your microSD card as a working, supplemental storage media but really, at some point you're just better off buying a new phone that already has a sizable about of internal storage,
And just a side note, if the playlist issue is really eating away at you there is the issue where Google has made a lot of changes to how we are allowed to interact with our microSD cards. It was at one time pretty much unrestricted but then some troubling security and privacy issue came into play so it became necessary for restricted access to specific folders along with limits on permission levels and such. So currently our apps we install typically only have access to corresponding and specific folders within the card. So in your case, if the Amazon Music app allows you redirect the save location for playlists, see using a that app's corresponding folder in your microSD card will work. The file path will likely be similar to SD card >> Android >> data >> com.amazon.music.xxxxx.xxxxx The exact file path and folder names used by your A20 will vary so adjust things accordingly. But within that app's assigned folder there was open permission levels for the app.
