You can convert a static ICL into a dynamic ICL.
You can update the fabric settings rack-mct-scheme on an already deployed fabric provided all the racks of
            the existing fabric have same ports participating in the ICL or MCT port-channel.
Ensure that the ICL or MCT LLDP ports of all the racks match exactly with the rack-mct-ports and rack-Id-mct-ports fabric
            setting. 
Shutdown or disable (lldp disable) the additional LLDP ports followed by fabric
                configure, and then re-attempt the static ICL to dynamic ICL conversion.
            Once the conversion is completed, bring up the additional LLDP links followed by
                fabric configure.

Note
When you modify the fabric settingrack-mct-scheme
                to "dynamic", the fabric setting rack-Id-mct-ports is
                reset to the empty string.