Not being able to easily transfer data between user account profiles is actually why I only use one Owner profile and compartmentalize my apps between trusted vs. untrusted using Shelter.
I wish I could take advantage of the amazing GOS additions made to user profiles instead of relying on Shelter, but this being so inconvenient to do while on the go keeps me on my current setup.
I wrote about my setup and reasoning of my setup here. If you need to transfer data across your compartments, perhaps you can consider a setup similar to mine until a better alternative is found.