How to initialize menu option PostSubmit to hide. 'data-hidden' doesn't seem to work.

nav.html

<template name="nav">
  <div data-id="nav"
       data-css="nav"
       data-view="toolbar">

    <div data-view="label"
         data-label="{{t9n 'app.displayName'}}"
         data-width=200>
    </div>

    <div data-view="menu">
      <ul data-view="data">
        <li data-id="menuHome"
            data-href="/">{{t9n 'nav.menu.home'}}
        </li>
        <li data-id="menuPrivate"
            data-href="{{pathFor 'postslist'}}">{{t9n 'nav.menu.postsList'}}
        </li>
        <li data-id="menuSubmit"
            data-hidden=1
            data-href="{{pathFor 'postSubmit'}}">{{t9n 'nav.menu.postSubmit'}}
        </li>
      </ul>
    </div>

    {{>navButton}}
  </div>

</template>

nav_button.js

'use strict';

Template.navButton.helpers({
  text: function(){
    var key = Meteor.userId() ?
        WebixDefaults.texts.navSignOut : WebixDefaults.texts.navSignIn;
    var text =T9n.get(key);
    if ($$('nav-button')) {
      $$('nav-button').define('label',text);
      $$('nav-button').refresh();
    }
    return text;
  },
  dataClick: function() {
    return `
    if (!Meteor.userId()){
      Router.go('/signin');
    } else {
      Meteor.logout(function() {
        Router.go('/');
      });
    }`
  }
})