I got an issue with that question.
I've make this to render a "string" for a ManyToMany relation :
->formatValue(function ($value, $entity) {
return implode(",",$entity->getCategories()->toArray());
})
and it works pretty good ! But I've a question !
How can I render many badges in Index ? Because this method render one unique badge with "Value 1, Value 2"... And I want to see 2 badges, one with "Value 1" and one other with "Value 2" in the same line. Someone know how to do that ?
I hope my question is clear. Noé