I'm not sure if this answers your Q, but I also hold my tune files on W10 (I have over 4000 of them ) - I notate them using MuseScore and save a copy as a .pdf file in a folder listed in the directory. These can then be imported into Mobile Sheets Pro via the Companion app. I do them singly, but I assume the Batch Import facility allows you to transfer a lot in one go. Like you, I also use more than one tablet: I have MSP installed on a second Acer Android tablet as a spare in case of failure of Acer No. 1, so once the collection has been loaded on No. 1, I make a backup, save it on the PC and carry out a 'restore' on tablet No. 2. The same process (i.e. 'restore' from a current backup) is used when my band colleagues need to update the revised tune collection on their tablets - which also have MSP installed - to ensure we all have the latest versions of the material.
You don't mention the format in which your files are saved on W10, but I hope the above is useful.
You don't mention the format in which your files are saved on W10, but I hope the above is useful.