When contacts are added to the Favorites on the LG phone, they are displayed with priority, so a new category with Favorites is displayed at the top of the Contacts app. Favorite contacts are also preferred in the Share function.

Android 9 | LG UX 9.0
Step 1:  Open the  Contacts -App
Step 2:  Tap on desired  Contact
Step 3:  Tap on  Mark as Favorite
  1. Open the Contacts-App
  2. Tap on desired Contact
  3. Tap on Mark as Favorite

LG Instructions