ActivityTimeline Admin users have the possibility to manage the appearance of the items on the timeline panel as well as what information to display on those items.
In Configuration → Issues → Issue appearance you can choose which icons to display on the issue bar, so hide everything that is not important to you:
You can also display 3 additional fields on the issue bar, these can be fields like Assignee, label, Component, and Jira Custom fields:
The same can be configured for Local Events in Configuration → Events → Event Appearance:
