You have the window set to hide on close and are always creating the window in "showAll". If you are changing the default close action from destroy to hide then you need to check if it already exists before creating it. If it already exists then show it.
Updated showAll method
Code:
function showAll()
{
var editWindow = Ext.ComponentQuery.query('#editWindow')[0];
//create the edit window if it doesn't already exist
//
if (Ext.isEmpty(editWindow)){
editWindow = Ext.create('myWindow');
}
editWindow.show();
}
Added item identifier to the edit window
Code:
Ext.define('myWindow',{
extend: 'Ext.window.Window',
itemId : 'editWindow', //added item id to the window for component query
eduType: 'myWin',
Fiddle