We have created a custom activity (Portal Message) which appears on the Activities Timeline in the Case Form.
However, the way it is displayed is confusing, because the Timeline shows: "Portal Message from <Owner>".
I would like to change this to "Portal Message from <Sender>". Otherwise it always seems as if the message was sent by the owner of the activity, which is not the case.

I know that customization options on timelines are limited, but is any way to accomplish this?

Thanks in advance,