1. From Setup, at the top of the page, select Object Manager.
2. Click Task.
3. Click Compact Layouts.
4. Click New. If you’ve already created a custom compact layout for tasks, select it.
5. If you’re creating a new compact layout, enter a name and label for it.
6. Select the task fields you want to display on the activity timeline.
7. Click Save.
8. Click Compact Layout Assignment.
9. Click Edit Assignment.
10. Select the new or updated layout.
11. Click Save.