[lvr123]

You're right. This isn't a trivial addition. But no so complex. I guess it could be added in a more general feature that would parse filenames in order to extract meta-data. Such as proposed in this post Import / Parsing filenames. For this latter, an easy workaround exists (a PowerShell script (that I'll be sharing soon) that copies all the files to the MobileSheetPro expected folder structure). But not for the grouping, as this feature does not exist. I haven't find a workaround until now.
For your info, the "-" is the separator used by MuseScore when exporting a score and its "parts" to PDF. It might be a common one in other Score editors.