How Add a widget to relationManager form

Is there a way to add a widget to the forms of a RelationManager?
I have attached a widget to a resource form through the EditPage:

protected function getFooterWidgets(): array  {
   return [
      \App\Filament\Widgets\Comments::class
  ];
}

protected function getFooterWidgets(): array  {
   return [
      \App\Filament\Widgets\Comments::class
  ];
}

This works so I added this method to the RelationManager.
no error and no widget.
Looking in Filament

RelationManager.php

RelationManager.php

there is no mention of widgets like there is in

Resource.php

Resource.php

.

So what to try next?