AFAIK you can use <% my_map = assigns.x.y.z.my_map %>:
def render(assigns), do: ~L"""
<section id="<%= assigns.x.id %>">
<% m = assigns.x.y.z.my_map %>
<ul>
<li><%= m.foo %></li>
<li><%= m.bar %></li>
<li><%= parse_qux(m.qux) %></li>
</ul>
</section>
"""
