New Idea
Internal Attendees on Timeline Activity for Non-Salesforce Users
From what I can tell, it doesn't seem like you can include anyone on the Internal Attendee's section when logging a call in Timeline (please correct me if I'm wrong here). It would be nice to be able to do so for cases when someone without a SFDC account (e.g. a Product Manager, Engineer, etc) is on a call with a customer.