Form builder in Symfony is very powerfurl, you can easily build complex forms.

One of the best option is CollectionType, it means you can embed a collection of subforms (or Entities related) into a main form.

According to this documentation : https://symfony.com/doc/3.4/form/form_customization.html#how-to-customize-a-collection-prototype, you can customize displaying.
But, this documentation disappeared in Symfony 4.

To quickly display a collection into a very complex layout, you can use Twig blocks extensions, or directly customize your view.

Let’s suppose we have this form :

class TaskListType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options = array())
    {
        $builder->add('tasks', CollectionType::class, array(
            'entry_type' => TaskType::class,
        ));
    }
}

class TaskType
{
    public function buildForm(FormBuilderInterface $builder, array $options = array())
    {
        $builder
             ->add('content')
             ->add('active', CheckboxType::class);
    }
}

You can use these blocks to customize the layout :

{% block _task_list_entry_tasks_widget %}
      {# collection widgets of TaskType #}
{% endblock %}
{% block _task_list_entry_tasks_entry_widget %}
      {# inner label of TaskType #}
{% endblock %}
{% block _task_list_entry_tasks_entry_content_widget %}
      {# field content of TaskType #}
{% endblock %}
{% block _task_list_entry_tasks_entry_content_label %}
      {# label content of TaskType #}
{% endblock %}

Or in your view :

{% for task in formTaskList.tasks %}
    <div class="form-group row align-items-center">
        <label class="col-md-3 label-control">
            {# access task data using task.vars.data #}
            Task {{ task.vars.data['id'] }}
        </label>
        <div class="col-md-6">
            {{ form_widget(task.children.content) }}
        </div>
        <div class="col-md-1">
            {{ form_widget(task.children.active) }}
        </div>
    </div>
{% endfor %}

And if you need to pass options of the main form to the child form :

class TaskListType extends AbstractType 
{  
     public function buildForm(FormBuilderInterface $builder, array $options = array())  
     {  
          $builder->add('tasks', CollectionType::class, array(  
               'entry_type' => TaskType::class, 
               'entry_options' => [
                   'label' => null,
                   // access $options['colorsList'] in TaskType
                   'colorsList' => $options['colorsList']
                ],
          ));  
     } 
}