Disable a panel conditionnaly in window->extensions menu

The following code I think is pretty clear.

//////////////////////////////////////////////////////////////////
// MenuDemo.jsx By Trevor http://creative-scripts.com 12 Apr 18 //
// Demonstrates how to control menu items on InDesign           //
//////////////////////////////////////////////////////////////////
#targetengine foo
// If using CSTK best to comment out the targetengine line
// Look at the bottom of the "Layout" menu
var installMenuItem;
/**
* [installMenuItem description]                Helper function for adding InDesign menu items by Trevor http://creative-scripts.com
* @param  {String}              title          The words you want displayed
* @param  {DOM Menu / Sub-menu} parentMenu     The menu / sub-menu on which the item should appear
* @param  {Function}            beforeDisplay  like function(ev){ev.target.enabled = !!app.properties.activeDocument}
* @param  {Function}            onInvoke       like
*                                              function(ev){
*                                                  ev.target.title =
*                                                      (app.properties.activeDocument && app.properties.activeDocument.name) || 'Nope';
*                                              }
* @param  {DOM Constant}        position       LocationOptions.BEFORE, LocationOptions.AFTER, LocationOptions.AT_END,
*                                              LocationOptions.AT_BEGINNING, or LocationOptions.UNKNOWN
*                                              [Optional] default LocationOptions.AT_END
* @param  {DOM Menu / Sub-menu / Menu Item} reference     [description]
*                                              [Optional] only needed if position is set to LocationOptions.BEFORE or LocationOptions.AFTER
* @return {DOM menuAction}                     The created or existing menu Item
*/
installMenuItem = function(title, parentMenu, beforeDisplay, onInvoke, name, position, reference) {
    var menuAction;
    if (typeof title === 'object') {
        parentMenu = title.parentMenu;
        beforeDisplay = title.beforeDisplay;
        onInvoke = title.onInvoke;
        position = title.position;
        reference = title.reference;
        name = title.name || title.title;
        title = title.title || title.name;
    }
    position = position || LocationOptions.AT_END;
    parentMenu = parentMenu || app.menus.item("$ID/Main");
    menuAction = app.scriptMenuActions.add({ title: title, name: name });
    if (beforeDisplay) {
        menuAction.eventListeners.add('beforeDisplay', beforeDisplay);
    }
    if (onInvoke) {
        menuAction.eventListeners.add('onInvoke', onInvoke);
    }
    return parentMenu.menuItems.add(menuAction, position, reference);
};
/*
 ____   __   _  _  ____  __    ____    _  _  ____   __    ___  ____
/ ___) / _\ ( \/ )(  _ \(  )  (  __)  / )( \/ ___) / _\  / __)(  __)
\___ \/    \/ \/ \ ) __// (_/\ ) _)   ) \/ (\___ \/    \( (_ \ ) _)
(____/\_/\_/\_)(_/(__)  \____/(____)  \____/(____/\_/\_/ \___/(____)
*/
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// This should add a "FabScript" submenu to the bottom of the "Layout" menu                                       //
// It contains to menu items                                                                                      //
// Demonstrates how to change properties of the menu items like their text and enabled status                     //
// Keep playing with the menu until you understand how it's actions fit in with the code.                         //
// To remove the menu use either foo.remove() from the correct scriptEngine or use from any engine                //
// app.menus.itemByName('$ID/Main').submenus.itemByName('$ID/&Layout').submenus.itemByName('FabScript').remove(); //
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
var foo;
foo = (function() {
    var toggleScriptEnable, toggleYepNopeTitle, yepNopeBeforeDisplay, enableMyScriptOnInvoke, yepNopeOnInvoke, wl, say, count;
    count = 0;
    toggleScriptEnable = toggleYepNopeTitle = false;
    /*
         _  _     _                 ___             _   _
        | || |___| |_ __  ___ _ _  | __|  _ _ _  __| |_(_)___ _ _  ___
        | __ / -_) | '_ \/ -_) '_| | _| || | ' \/ _|  _| / _ \ ' \(_-<
        |_||_\___|_| .__/\___|_|   |_| \_,_|_||_\__|\__|_\___/_||_/__/
                   |_|
    */
    /**
     * [wl description]         Shortcut to output to either ESTK or CSTK console, applying / filtering the css
     * @param  {String} message
     * @param  {String} css     [Optional] css to be applied to the message if sent to the CSTK console
     * @return {String}         The message without the css
     */
    wl = function(message, css) {
        if ($.engineName === 'CSTK') {
            $.writeln(message, css);
        } else {
            $.writeln(message);
        }
        return message;
    };
    /**
     * [say description]        Speaks the message out and passes the message out so it can be forwarded to a log etc.
     * @param  {String} message the message to say
     * @return {String}         The message
     */
    say = function(message) {
        const DONTSAY = false; // Change to true to shut the computers mouth
        if (DONTSAY) { return message; }
        var isMac, script;
        isMac = $.os[0] === 'M';
        script = (isMac ? 'Say "' : 'CreateObject("sapi.spvoice").Speak "')  + message + '"';
        app.doScript(script, ScriptLanguage[isMac ? 'APPLESCRIPT_LANGUAGE' : 'VISUAL_BASIC']);
        return message;
    };
    /*
     __  __                                _   _    _    _
    |  \/  |___ _ _ _  _   _____ _____ _ _| |_| |  (_)__| |_ ___ _ _  ___ _ _ ___
    | |\/| / -_) ' \ || | / -_) V / -_) ' \  _| |__| (_-<  _/ -_) ' \/ -_) '_(_-<
    |_|  |_\___|_||_\_,_| \___|\_/\___|_||_\__|____|_/__/\__\___|_||_\___|_| /__/
    */
    enableMyScriptOnInvoke = function(ev) {
        wl(say('On Invoke ' + ev.target.name), 'color: blue;background:yellow;');
        ev.target.title = ev.target.name = toggleScriptEnable ? 'Enable my script' : 'Dis-enable my script'; // ;-);
        toggleScriptEnable = !toggleScriptEnable;
    };
    yepNopeBeforeDisplay = function(ev) {
        count++;
        ev.target.enabled = toggleScriptEnable; // toggleScriptEnable
        ev.target.name = count + // increments on beforeDisplay events
            (toggleYepNopeTitle ? ' Yep script' : ' Nope script') + // toggles on beforeDisplay events
            (toggleScriptEnable ? ' is enabled' : ' is not enabled'); // changes on the enableMyScriptOnInvoke event
        ////////////////////////////////////////////////////////////////////
        // NOTE: The Yep and Nope are not connected to the enabled status //
        // take note of when they swap and when the count changes         //
        ////////////////////////////////////////////////////////////////////
        toggleYepNopeTitle = !toggleYepNopeTitle;
        wl(say('Before display ' + ev.target.name), 'color: orange');
        // NOTE: The before display is triggered when the menu item is invoked and before the parent menu is displayed
        // In this example the parent menu is the "Layout" menu
    };
    yepNopeOnInvoke = function(ev) {
        wl(say('On Invoke ' + ev.target.name), 'color: red;background:yellow;');
        ///////////////////////////////////////////////////////////////////////////////////////////////////////
        // NOTE: before the onInvoke fires the beforeDisplay will fire                                       //
        // This is in addition to the beforeDisplay that fired on displaying the menu                        //
        // In our case this will cause that it looks like the Yep Nope are not being toggled                 //
        // To circumvent that one could place in the on Invoke `toggleYepNopeTitle = !toggleYepNopeTitle;`   //
        // Take note that the count changes with the onInvoke because of it's associated beforeDisplay event //
        ///////////////////////////////////////////////////////////////////////////////////////////////////////
    };
    /*
       _      _    _   __  __
      /_\  __| |__| | |  \/  |___ _ _ _  _ ___
     / _ \/ _` / _` | | |\/| / -_) ' \ || (_-<
    /_/ \_\__,_\__,_| |_|  |_\___|_||_\_,_/__/
    */
    var fooMenu = app.menus.itemByName('$ID/Main').submenus.itemByName('$ID/&Layout').submenus.itemByName('FabScript');
    // For convenience we shall remove the menu if it already exists.
    if (fooMenu !== null) fooMenu.remove();
    // Add the FabScript submenu
    fooMenu = app.menus.itemByName('$ID/Main').submenus.itemByName('$ID/&Layout').submenus.add('FabScript', LocationOptions.AT_END);
    // Add the menu items with the event listeners
    installMenuItem({
        name: 'YepNope',
        parentMenu: fooMenu,
        onInvoke: yepNopeOnInvoke,
        beforeDisplay: yepNopeBeforeDisplay
    });
    installMenuItem({
        name: 'Enable my script',
        parentMenu: fooMenu,
        onInvoke: enableMyScriptOnInvoke
    });
    return fooMenu;
})();
/*
To remove the menu
foo.remove();
or
app.menus.itemByName('$ID/Main').submenus.itemByName('$ID/&Layout').submenus.itemByName('FabScript').remove();
*/