Example code for custom entity form mode

There are many examples of how to create custom form modes in die UI, and how to invoke them programmatically, but I’m looking for an example of how to create a custom view mode for an entity form. Could someone point me to a core.entity_form_display.node.bundle.mode.yml file where mode IS NOT default?

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Source: https://www.drupal.org/taxonomy/term/4/feed