As per https://www.drupal.org/node/3375748 → , usage of translatable string for field type definition category is deprecated.
Check the RelationshipEntityReferenceItem class annotation:
/**
* Defines the 'group_relationship_target' entity field type.
*
* Extends EntityReferenceItem to dynamically support config entities.
*
* @FieldType(
* id = "group_relationship_target",
* label = @Translation("Group relationship target"),
* description = @Translation("A reference to either a content or wrapped config entity."),
* category = @Translation("Reference"),
* default_widget = "entity_reference_autocomplete",
* default_formatter = "entity_reference_label",
* list_class = "\Drupal\Core\Field\EntityReferenceFieldItemList",
* no_ui = TRUE,
* )
*/
Replace the translated category property with:
category = "reference",
Fix and commit.
The Relationship Entity Reference field type will appear under Reference category in new field creation UI.
None.
None.
Needs review
2.2
Code
FWIW, defining this on a no_ui field type is pretty pointless, since the category is for the ui, which is disabled here, so the best option might be to just remove it, no concerns about backward compatibility then, but I guess you already require a recent version anyway.