Favourites are displayed at the top of the Contacts app on your Samsung device, but it's not only in the Contacts app that favourites are placed at the top of the list; they are also displayed in the Phone app, for example.

The instructions show how to add a contact to the favorites and how to remove the contact from the favorites.

Android 10 (One UI 2.0)
Step 1:  Open the  Contacts -App
Step 2:  Tap on desired  Contact
Step 3:  Tap on  Favorite
  1. Open the Contacts-App
  2. Tap on desired Contact
  3. Tap on Favorite

Samsung Instructions