Can the Transfer Tool transfer more than one cPanel account at once?
Yes, cPanel can transfer a maximum of 5 accounts at one time.
There is an option labeled "Transfer Threads" in the Transfer Tool. This option defaults to 5 which means that a maximum of 5 accounts can be transferred at once. You may lower this option to reduce the number of accounts transferred at one time.
It is important to also note that this option is a maximum, not a hard configuration. cPanel continually analyzes the server's resource usage during the transfer and will automatically reduce the number of simultaneous transfers if too many resources are being used.
If the Transfer Threads option is set to 5 and you notice that the server is only transferring 1 account at a time, that means that cPanel has detected that there are only enough server resources to transfer a single account without sacrificing server performance and/or stability.
This information also applies to the "Restore Threads" option as well, although the restoration processes exist on the destination server, and the transfer processes exist on the source server.