I quickly browsed Amazon's documentation for AWS Transfer for SFTP, and unfortunately it looks like this AWS service does not include a way to adjust any of the technical settings of the SFTP/SSHD service. So there is no way to enable SSH server-side keepalives (which is what the "client alive interval" setting does) in AWS Transfer for SFTP.
Your only choice would be to contact Amazon AWS support, tell them about your requirement and perhaps register a "wishlist" item for future development of this service.
However, you might wish to talk to your network administrator to find out the reason why your SFTP connections are disconnecting. If your site has a firewall with an overly strict connection idle timeout policy, the firewall might be the one breaking the connections. If there were no firewalls and no network problems, an idle SFTP connection should in theory stay alive indefinitely.
(Sometimes such a strict idle timeout policy indicates the firewall's performance does not quite meet the demands placed to it: if a firewall is getting overloaded, more aggressive reaping of old connections is one way to work around it without adding new firewall hardware. But 3 or 4 minutes is in my opinion excessively strict.)