In addition to predefined groups, you can also create your own groups for contacts by selecting which account to create the group in.

Android 10 | ColorOS 7.0
Step 1:  Open the  Contacts -App
Step 2:  Open the  Menu
Step 3:  Tap on  My Groups
Step 4:  Tap on  Add
Step 5:  Select an desired  Account
Step 6:  Enter a  Group Name  and tap on  Save
Step 7:  Select desired  Members
Step 8:  Tap on  Add
  1. Open the Contacts-App
  2. Open the Menu
  3. Tap on My Groups
  4. Tap on Add
  5. Select an desired Account
  6. Enter a Group Name and tap on Save
  7. Select desired Members
  8. Tap on Add

Oppo Instructions