You can now customize your Dynamic Highlights Panels to include the standard Follow button. Expose the Follow button by using the Lightning App Builder so users can easily subscribe to updates on key records. The button is hidden by default.
Where: This change applies to Lightning Experience in Group, Essentials, Professional, Enterprise, Performance, Unlimited, and Developer editions.
How: In the Lightning App Builder, select the Dynamic Highlights Panel component on the canvas. In the properties pane, select or deselect Hide Follow/Unfollow button to control whether the button is visible to your users.