You can add a port to be scanned, by using the "ADD" method.
Normally, when adding a port, no scan protocols are defined, and no scans are performed on that port, pending further configuration. However, if you wish to specify that the proxy scanning engine should scan for all known protocols, without having to issue separate commands, you could use the "scan-all" keyword.
/as security proxycheck port 80 add scan-all
/as security proxycheck port 1080 add