Reusing Swing UI to make other UIs

I’m developing an application that has lots of dialogs that shares the same general layout, so I’m trying to find a way to reuse this general layout to avoid having to copy-paste it too many times. I’m using NetBeans’ GUI Builder to design my GUI.

First I thought about using inheritance, so I made a DialogTemplate class and made my modals inherit it, running it does work, but I can’t see it on NetBeans’ GUI editor. Another option I tried was to make this template a component and include it in my modals, but in this case I can’t add components to it.

Is there any other option, or what am I doing wrong?

Thanks in advance.