In the Timeline configuration, click on the '+' icon below "Related Object"

Select the object from the list for which you want to configure the timeline

Provide a header and sub-header for the timeline

Select the date field from the list

Choose an icon for the timeline from the icon library

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Select the fields from "Additional Fields" to display on the timeline and click the "Add" button

Now, you will be able to see the configured object records on the timeline in the preview section