search-morph.md

Within comment resource

public static $searchRelations = [
    'post' => ['title'],
    'video' => ['title'],
];

And here is the comment model

class Comment {

    public function commentable() {
        return $this->morphTo();
    }
    
    public function post() {
      return $this
        ->belongsTo('App\Post', 'commentable_id')
        ->where('commentable_type', 'App\Post');
    }
    
    public function video() {
      return $this
        ->belongsTo('App\Video', 'commentable_id')
        ->where('commentable_type', 'App\Video');
    }
}