Up till now the WinForms Generator had no way of assigning keyboard shortcuts to Menu Items from an attribute in a YAML file.
(The WinForms Generator automatically does create keyboard shortcuts for some pre-defined and hard-coded Menu Items, such as File->Save and some Edit-> find commands, though).
As of trunk Rev. 2813 (Jan. 27th, 2015) the WinForms Generator supports a new Attribute for mni Elements, 'ShortcutKeys'.
Documentation for that can be found here: