Requires CC V5.1.1 and later and calibre 2.54 and later
If CC and calibre are new enough then the CC can show custom "columns built from other column" (composite columns) in the top-level display of the Cloud Connection. CC requires that the values be stored in the calibre database by an optional calibre plugin. The plugin, a Library Closed plugin named Save Composite Custom Columns, is available in this MobileRead post, in calibre's Index of Plugins page and through calibre's Get Plugins feature (Preferences / Plugins / Get new plugins).
After you install the plugin in calibre then open your library in calibre's GUI. When you close the library (the GUI) the plugin will save the information. You will see a notification while calibre is closing. Next do whatever you normally do to sync your library with the cloud provider. The next time CC opens that cloud library you will see the composite columns listed in the top-level display. The plugin will run every time you close your library so that the information in CC will be up-to-date.
If the plugin is not installed or has not run then you will not see the composite columns.
Note: the plugin is not run when you use calibre's command line to modify metadata for books. You must run the calibre GUI to run the plugin and update the information.