3PC and Custom Multi Item TV: need help and advice

Picman.TV = function(config){
    config = config || {};  
    Ext.applyIf(config,{
        layout: 'form',
        autoHeight: true,
        defaults: {
            border: false
        },
        forceLayout: true,
        renderTo: 'tv'+config.tv+'-form',
        items: [{
            xtype: 'modx-tabs',
            id: 'tvtabs',
            activeItem: 0,
            activeTab: 0,
            defaults: {
                border: false, 
                autoHeight: true
            },
            border: true,
            items: [{
                title:'item',   
                defaults: {autoHeight: true},
                items: [{
                    html: 'tab1 ',
                    items: [{
                        xtype: 'picman-tvgrid', // grid filled with data from custom table
                        preventRender: true
                    },{
                        // here a form to load the values from the item selected in the grid
                        //I suppose I need a new xtype (picman-tvform) to hold the form
                    }]
                    
                }]            
            }]
        
        }] ,
        tbar: [{
            text: 'Add a tab',
            handler: this.addTab // Add a tab with same structure as tab1
        }]
    });
    Picman.TV.superclass.constructor.call(this,config);
}
Ext.extend(Picman.TV,MODx.Panel,{
    addTab: function (){
        // how to know how many tabs are already there ?
        // how to know on which tab am I ?
        // how to add the tab ?
        // I want the added tab have the same structure as the first tab 
    }
});
Ext.reg('picman-panel-tv',Picman.TV);