Can an instant support technician transfer files?

Yes, in either direction, when connecting to an end user on Windows or Mac. The end user cannot see file transfer operations being performed, but is notified they are happening via the chat/activity log.

The technician should click the Transfer files button on the VNC Viewer session toolbar:

The Remote file browser dialog opens. The technician can upload files and folders to the remote computer, or download files and folders from it.