something here
{{ block body }}{{endblock}}
something here

extends layout.html.twig
{{block body}}
modify user settings form
{{endblock}}

something here
{{ block body }}{{endblock}}
something here

extends layout.html.twig
{{ block body }}
some specific section things here
now the form
{{ block body }}{{endblock}}
{{endblock}}

extends settings.html.twig
{{block body}}
modify user settings form
{{endblock}}

something here
{{ block body }}{{endblock}}
something here

extends layout.html.twig
{{ block body }}
some specific section things here
now the form
{{ block form }}{{endblock}}
{{endblock}}

extends settings.html.twig
{{block form}}
modify user settings form
{{endblock}}

{% extends 'yourBundle::layout.html.twig' %}
{% include "yourBundle::settings.html.twig" %}
{{block form}}
modify user settings form
{{endblock}}