When Importing KeyPay Data, Can A User With Shared Permission Work In It At The Same Time?

No, the status will show as File in Use as soon as you click the Import button, and while the revision is being created in File Manager with your imported data.

The file will only be available to be accessed as Read Only until the import has completed.

Whilst you are completing the Integration setup and Payroll setup, you can have your file open and so can another user. However, you will not be able to import any data until the file is closed.