[Answer]-How to show some elements after hiding everything? Toggling isn't working

You can’t declare class twice in an element but you can space separate as many class names as you want

<div class="jumbotron" id="{{post.id}}" class="parent{{post.parent_simpler}}">

Should be :

<div class="jumbotron  parent{{post.parent_simpler}}" id="{{post.id}}">

You can confirm this by inspecting the live html in browser developer tools, only one declaration is being recognized