[Zubersoft]

There is an option to update the existing song if you import a file that will be copied to the location of an existing file. It all depends upon your storage settings and how you are managing your files/folders. If you use all the default storage settings and you import file "abc.cho", then you make modifications and import "abc.cho" again, it should present an option to "Update Existing Song with New File". This will replace the existing file and update the existing song instead of creating a new one. You can also long press a song on the library screen, tap the three dots at the top right and select "Swap File". This can be used to replace a file for an existing song. 

If you import a file that matches an existing song's file and you select "overwrite", that will overwrite the existing file, but create a new song, so that's not what you typically want to do. I'm going to be making changes to how this is handled in the near future, as it seems to confuse a lot of people. The reason it doesn't work the way you expect is that there is not a one to one correlation between files and songs, you can reuse the same file for multiple songs, and some users have files with identical names in their library stored in different folders and tied to different songs. Due to this, MobileSheetsPro can't assume you want to update an existing song if you import a file that happens to match the name/path of an existing file in the library (although I'm going to make that the most prevalent option in the future).

Mike