Form ready / init event on Ninja Forms - Backbone / Marionette

I am currently working with the "NinjaForms" plugin for WordPress, which provides custom form management for the backend. It's based on Marionette / Backbone JS. After some research, I had no problem triggering JavaScript functions on input change and on form submit. However, I have not found a way to fish for an event once the form is initialised / rendered / shown (any of these, really).

What I am doing right now is initialising a Marionette object, adding listeners to a radio and then adding functions to execute it on event:

if(typeof Marionette !== 'undefined') {
    var mySubmitController = Marionette.Object.extend( {
        initialize: function() {
            // init listener
            this.listenTo( Backbone.Radio.channel( 'forms' ), 'view:show', this.initAction);
            // field change listener
            this.listenTo( Backbone.Radio.channel( 'fields' ), 'change:modelValue', this.valueChanged);
            // submit listener
            this.listenTo( Backbone.Radio.channel( 'forms' ), 'submit:response', this.actionSubmit );
        },

        // init action
        initAction: function() {
            console.log("init");
        },

        // input update action
        valueChanged: function(model) {
            console.log("update");
        },

        // submit action
        actionSubmit: function( response ) {
            // handled via php

            console.log("submit");
        },
    });

    // initialise listening controller for ninja form
    new mySubmitController();
}

However, the line this.listenTo( Backbone.Radio.channel( 'forms' ), 'view:show', this.initAction); is not working. I have tried the events view:render, view:show, show:view, render:view without success.

I searched in the Backbone / Marionette documentations, but could not find a fitting event. This question might be a duplicate, but I could not really find any topic regarding form initialisation events with Backbone.

after some long search, googling and frustration I've found a solution. Using the following JavaScript-Code, you can execute code on form render:

// if there is a ninja form on this page
if(typeof Marionette !== 'undefined') {
    var mySubmitController = Marionette.Object.extend( {
        initialize: function() {
            // init listener
            this.listenTo( nfRadio.channel( 'form' ), 'render:view', this.initAction );
        },

        // init action
        initAction: function() {
            // code to execute on form render
        },
    });

    // initialise listening controller for ninja form
    new mySubmitController();
}