Currently there's no formatting support for twig. Using ctrl + k + d to format the document removes tabs/spaces within {% %} blocks. This leaves me with code such as

<div class="row form-cost">
    <div class="col-sm-3">{{ form_widget(form.amount) }}</div>
    <div class="col-sm-3">{{ form_widget(form.price) }}</div>
    <div class="col-sm-3">
        <input type="text" disabled value="{{ form.vars.value.total|number_format }}€" class="form-control">
    </div>
    <div class="col-sm-3">{{ form_widget(form.note) }}</div>
</div>
{% endblock %}
{% block _training_price_row %}
{{ form_row(form) }}
{% set training = form.parent.vars.value %}
{% set length = training.event.dates|length %}
{% embed "Form/element.html.twig" %}
{% block label %}
{{ 'form.duration'|trans }}
{% endblock %}
{% block content %}
{{ 'event.message.dates'|trans(count=length) }}
{% endblock %}
{% endembed %}
{% embed "Form/element.html.twig" %}
{% block label %}
{{ 'form.price'|trans }}
{% endblock %}
{% block content %}
{{ (length*training.price)|number_format }}€
{% endblock %}
{% endembed %}
{% embed "Form/element.html.twig" %}
{% block label %}
            Teilnehmer
{% endblock %}
{% block content %}
{{ training.countParticipants }}
{% endblock %}
{% endembed %}
{% endblock %}

Which is sadly absolutely unreadable. It also conmplains about "unexpected token" form_theme (which I think might be Symfony-specific).