We started using Associated Records on Timeline Entries to connect to CTAs. We would like the same CTA Association Indicator on the Timeline Activity list whether an Activity was created from within a CTA or If an existing Timeline Activity is associated after the fact. 

If a Timeline Activity is created from within a CTA - there is a visual indicator on the Timeline:  

If you associate an existing Activity to a CTA - there is no indicator:

Users have to open up the Timeline Entry and Scroll to the bottom of the activity in order to see that it is associated to a CTA:

The big use case for us is being able to connect Emails sent from Outlook using Gainsight Assist that land on the Timeline to CTAs.