You can copy the same Quicken file from one computer to the next. But you cannot use the solution simultaneously on both desktops. You have to install the software on the two devices and sign in with the same identification.
After logging in, if you want to move the file from Windows to Mac and vice versa, you must convert it. Avoid moving data often. If you must view a dossier on different computers, try using Quicken on the web.
Subscription users can access the latter on any desktop. You can use it to review accounts and move files without installing the software.