We can mark saved contacts on the Xiaomi device as favorites. Favorites are always displayed at the top of the Contacts app. Favorite contacts can be dialed faster using the Phone app.

Note: To remove Favorites, tap the Favorites icon again.

Android 10 (MIUI 12.0)
Step 1:  Open the  Contacts app
Step 2:  Choose a  contact
Step 3:  Tap on  Favorite
  1. Open the Contacts app
  2. Choose a contact
  3. Tap on Favorite

Xiaomi Instructions