You can edit menu by dragging types and type instances from the Data types section on the left to the canvas in the middle.
To search for a data type, click on magnifying glass icon in the Data types section header.
You can expand categories and types by clicking located to the right of the category name.
Menu can have up to 3 levels.
You can define more than one menu. You select which menu should be used as a default in the settings. Currently selected default app menu is marked in the menu editor with the red color. You can also instruct the program to show a particular menu instead of the default one for a certain data type by setting a corresponding option in Preferences on the Data Type details page. Do not forget to press Save after introducing changes to the menu.
You can read more about the menu editor here.