For the document types available in the Visibility, Transparency and Communications menu you can refer to the table here: sfc2021-sd-prg-vtc.png (1050×822) (europa.eu).
The nomination of a comms officer is always CCI/programme-based, as they are nominated for each programme.
The nomination of a comms coordinator is MS based, ie. no specific CCI/programme to link it as it’s a national role.
If you have a nomination of a comms officer upcoming, then you should selected the comms officer document type (and then you will be able to enter the CCI number).