Hi @alain_miltenburg. I'm not sure if this is anything like you were looking for, but if you have ever looked into customizing the user interface by code, you may have already come across some of this. The UI customization generally starts with the Environment object. Then the Ribbon(s) and RadialMarkingMenus directly available within that specific environment. At the ribbon level, you also have access to the QuickAccessControls (CommandControls) which populate the Quick Access Toolbar. Then from the Ribbon, it steps down to RibbonTabs, RibbonTab, RibbonPanels, & RibbonPanel. Then the RibbonPanel can have CommandControls and/or SlideOutControls (more CommandControls). The CommandControls is where you have the different types of controls (buttons, button pop-up, combo box, gallery, macro, pop-up, separator, split button, and the like). Under those are the actual ControlDefinition objects.
Then on the RadialMarkingMenu side, you have the 'directional' controls, and the ability to create sub controls within a directional control. I honestly have not created any of my own Inventor add-ins yet, due to corporate restrictions and red tape, so I have not done a ton of UI customization of my own by code yet, but I have created my own panels and buttons before by code. I'm not really sure about how to display a specific RadialMarkingMenu in a specific location on the modeling screen yet, though. I hope this helps some.
Wesley Crihfield

(Not an Autodesk Employee)