By default, the Samsung device asks where to save a new contact each time you create one. You can choose to select the location as the default location or always be asked first. Once the default location is set, it can be changed in the contacts settings.

Android 10 (One UI 2.0)
Step 1:  Open the  Contacts -App
Step 2:  Open the  menu
Step 3:  Tap on  Manage contacts
Step 4:  Tap on  Default storage location
Step 5:  Choose desired  storage location
  1. Open the Contacts-App
  2. Open the menu
  3. Tap on Manage contacts
  4. Tap on Default storage location
  5. Choose desired storage location

Samsung Instructions