Simple to use templates for creating templates in unity
Simply drag the templates into:
*\Unity\Editor\Data\Resources\ScriptTemplates
After installation there will be and option for EditorWindow in left mouse click creation in Unity's assets folder
First Create an Editor Window Attribute Second Create an Editor Window
BOTH WITH SAME NAME
Now on Unity you can select your window on the Window tab, and inspect elements there are tagged with [YOUR_WINDOW_NAME]
Simply insert a function called "void On'YOUR_WINDOW_NAME'GUI ()" and it edit it just like you do on OnInspectorGUI()