For our Marketplace Partners we offer a couple of tools that enable you to create own add-ons.
Here you'll find the certification document with an introduction to marketplace Admin area and the necessary tools for deployment.
In the Marketplace Page https://marketplace.matrix42.com/partner-program we offer all necessary information. You receive access to that page once the partner agreement is signed.
As Partner you can also download the installation files of Matrix42 add-ons: https://marketplace.matrix42.com/customizing-apps/