Find a way to force Nickel to call loadView again (but this will be fragile).
Keep a reference to each menu and the added items so it can be removed and added again (threading makes this slightly more complicated, and what if a menu gets destroyed and the pointer becomes invalid...).
Restart Nickel (this has too much potential to break things, and it's overkill).
Rework the menu item injection so items can be modified just before the menu shows rather than when the view is initialized (this is probably the best option).
There are a few possible ways I could do this: