How do I add, change or remove a key command from an application's menu, or contextual menu, without any third party application?

Can I use something other than Cmd ⌘ with my trigger?

What if a menu item appears twice, like your Mailbox in Mail, which is at the bottom of several different menu structures?

Can I add a single key as a trigger, for instance just the number 1 , rather than use a modifier, such as Cmd ⌘ 1 ?

What if the menu item doesn't have a name - ie a Signature in Preview?

What if I need to add a key command to a menu whose title changes contextually?

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