@app.route('/test')
def test():
    test = ['a','b','c','d','e','f','g',['1','2','3']]
    return render_template('test.html',data=test)

{% for item in data %}
<tr>
  <td>{{item.0}}</td>
  <td>{{item.1}}</td>
  <td>{{item.2}}</td>
  <td>{{item.3}}</td>
  <td>{{item.4}}</td>
  <td>{{item.5}}</td>
  <td>{{item.6}}</td>
</tr>
<tr>
  <td colspan="5">{{ item[7][0]}}</td>
  <td>{{ item[7][1]}}</td>
  <td>{{ item[7][2]}}</td>
</tr>
{% endfor %}