[Blumi]

[...] I would instead suggest using the library synchronization feature and use the folder mapping feature to map file paths from one device to the desired file path on the other device (this is covered in the tutorial video on library synchronization: https://youtu.be/85EzubSZsZ8).

Thanks a million, Mike. You are my personal hero!
I just love Mobile Sheets (Pro) and I was convinced that there will be a solution to my problem.
Your solution proposal reaffirms my conviction that MobileSheets is the best app in this application area.