[Users] How to assign shortcut key?

[sylpheed at 911networks.com]

CM 3.15.1 on manjaro.

How do I assign a shortcut key to the:

Right click on the right border of the body of the message > Open

I receive a lot more of html emails, that I'd like to read in Chromium

I'd like to use the mouse less (I have an elbow injury)

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sknahT

vyS