CommandControls.AddComboBox() on UserInputEvents.OnLinearMarkingMenu E_NOTIMPL Not implemented exception

[Inventor30Dev]

Hello,

I am trying to AddComboBox() the linearMenu but i am getting E_NOTIMPL Not implemented exception.

Is there anything that i missed in the setup maybe? Or is it just not implemented in the Inventor API?

https://help.autodesk.com/view/INVNTOR/2020/ENU/?guid=GUID-B2999CA8-BF3B-4DB5-8CFC-5E9B8DFBC086

UserInputEvents.OnLinearMarkingMenu( SelectedEntities As ObjectsEnumerator, SelectionDevice As SelectionDeviceEnum, LinearMenu As CommandControls, AdditionalInfo As NameValueMap )
{
   LinearMenu.AddCombobox(myComboboxDefinition); //$exception {"	 (Exception from HRESULT: 0x80004001 (E_NOTIMPL))"}
}

The goal is to add a parent element to the LinearMenu, then have a dropdown menu from it displaying the children on the side. (Like in Windows when we rightclick on the desktop we can hover under "New"  from the dropdown menu, displaying us more options on the side like folder, shortcut, txt document etc in a separate dropdown.)

[JelteDeJong]

I expect that "E_NOTIMPL" means "NOT IMPLemented".

Also according to this post, it's not possible.