As an accountant, can I export my client's QB online file to QB desktop and still have my client work on their QB online account?

@aswoffice, you cannot use the 2 products simultaneously as data entered into one does not "sync" with the other.  

and the export to desktop is not complete nor accurate except for the most basic lemonade stand type business

https://community.intuit.com/articles/1145409-export-limitations

and if it was complete and accurate, you could not work in it and expect to upload it and your changes back to QBO without over writing all work entered while you had it.

QBO has an accountant log in, the user invites you