If you can edit data on NTFS from both operating systems then I would use NTFS as your data storage location for Manager.
The problem is that the c:\users%username% folder has permissions set to only allow that user on windows access.
The solution is to open Manager and change the data path location to say e:\Manager Data and make sure that everyone can write to that folder and obviously do the same thing in Linux. Then copy the data file to that folder.
Do not use a FAT32 USB Key unless you want to lose your data. USB keys should never be used to store vital data - you could lose the key, the key could get corrupted etc. In addition Fat 32 on USB keys tend to corrupt a lot more easily than NTFS. Get your data onto the hard drive as soon as possible.
For your particular situation I would recommend the cloud option as this will mean no loss of data, no data corruption etc. I would not be keen to try and edit vital data like that on two different operating systems all the time as something could go wrong. It shouldn’t but it can happen.
Also I wonder why you need to dual boot - if you want to use Linux, and are only booting for Windows Programs that cannot be used in Linux, I believe that Wine should solve those issue. There should not be any reason to dual boot.