[itsme]

As I understand ABC support will be part of the planned additional ChordPro features that are hopefully coming soon.

@RAc:
if storage space is really an important topic for you (I doubt it really is nowadays) you just have to manage your files yourself to avoid that MobileSheets makes a copy of every file.
Me, BRX and some other forum members do that without any problems.
"Manage files yourself" means:
on Android: uncheck "Let MobileSheets Manage My Files" and set the path where you want to store your files in "Set the MobileSheets Storage Location" in Settings - Storage
on WIndows: just set the MobileSheets storage location to a path outside of c:\Users\her\AppData\Local\Packages\41730Zubersoft.MobileSheets_ys1c8ct2g6ypr\LocalState\
on iPad: I'm not sure if managing files yourself is possible, BRX might know more

If you do that, you can store your files in a folder structure of your choice inside the MobileSheets storage location and MobileSheets will use them from the location where you stored them.
Just in case you import a file from "outside", MobileSheets has to make a copy.

The main advantage for me is that any edits, no matter if they are done with MobileSheets or with any external editor show up immediately in MobileSheets without the need to re-import or apply "Swap File". Saving storage space is a nice secondary effect, but not my main concern.