pass block into embed and forward to another embed? I'm trying to achieve some modularity using embeds, but with the possiblity to extend/inject customizations from the including template. 

Consider the following scenario:

Have a modular partial which contains a form, say form.twig
I want the ability to add new form fields at the end of the form, but using the otherwise common form.twig, so I add a {% block form_extension %} in form.twig

I have another page template, that includes/embed that partial, say page.twig. Now, this works, I just add a block when embedding, and it gets injected.

But, I also have another modular partial, say partial_with_form.twig, that embeds form.twig. And I want to be able to define the form_extension block, when embedding partial_with_form. 

Is this even possible? I have tried with parent() and block(), but none of them can give me the content of the supplied block unless I specify the targeting block in partial_with_form. But then it will be outputted there...
If partial_with_form.twig isn’t making any of its own customizations to form.twig, then I’d just include the form.twig template using an {% include %} tag, and wrap that whole thing with a {% block %}, so if a template wants to include the partial and make changes to the form, they can just redefine the form themselves.

partial_with_form.twig:

{% block form %}
  {% include 'form' %}
{% endblock %}


Other template:

{% embed `partial_with_form` %}
  {% block form %}
    {% embed 'form' %}
      {% block form_extension %}
        &lt;!-- ... --&gt;
      {% endblock %}
    {% endembed %}
  {% endblock %}
{% endembed %}