To create a Design, you have to go on Parameters and then in Interface. 

You will find on the right a Design box where you will be able to modify, deleate or create your design. When you are creating a design, be aware that the code is not important. It is just used for your information.

When you think that your design is complete, go to Lenses and choose the one desired. You can also apply it in multi update. 

In General tab, you will find a Design line where you can choose the desired one via the drop-down menu or create one via the blue shortcut button.