Hi Community!
I have made custom fields to the Phone Call entity (a disposition field with an option set) and in order for the new field to appear in the timeline view of leads, I added the new field to the Phone Call Card form:

...and changed the record that appears in the timeline to the Phone Call Card form:

Everything seemed to work, except now for some reason the time stamp has been replaced with what appears to be the Regarding field. I have not been able to locate where to edit this field:

So I'd be happy to either go back to the default form for phone calls in the timeline as long as I can add the new Disposition field to that, or change the Phone Call Card form so that the time stamp shows instead of the regarding field in the screenshot above.