According to Localize the accelerators,
Keyboard accelerators are implemented as virtual-keys. Localized accelerators must be chosen from the predefined collection of Virtual-Key codes (otherwise, a XAML parser error will occur).
and
VK_OEM_PLUS | 0xBB | For any country/region, the + key |
---|
You can set VK_OEM_PLUS programmatically.
myButton.KeyboardAccelerators.Add(new Microsoft.UI.Xaml.Input.KeyboardAccelerator()
{
Key = (Windows.System.VirtualKey)0xBB,
Modifiers = Windows.System.VirtualKeyModifiers.Control
});