You can import csv and ldif addressbooks and also directly involve the Gmail addressbook. I cannot speak to Comcast. Clicking an addressbook there is a three dot menu to the right that shows import options, and with Carddav menu, you can llink Gmail directly.

Thanks for the info. Pointed me in the right direction for Comcast, still working on the gmail linkage - which seemed successful while setting it up, but results were nil. D.

There is a Carddav option on the 'create new addressbook' icon in addressbook pane. Click that and enter your gmail email address and I think the setup will continue from there.