Entity form modes

This sandbox is bringing the concept of "form mode" to forms which is the same pattern as view modes but applied to the edition forms.
As is you have to export the form mode as part of a field definition to set the widget it should use in a given form mode.

Example:

[...]
      'forms' => array(
        'description_form' => array(
          'type' => 'field_extrawidgets_hidden',
          'weight' => 8,
        ),
      ),
[...]

There is no UI but it could be interesting to bring one like in core for Drupal 8. :)