There isn't anything exposed in Xrm.Page that would allow you to interact with the ribbon buttons in a supported way. I supposed it would be possible to use some unsupported code to potentially do something but really it wouldn't be worth the hassle when
you could use a tool like
Ribbon Workbench to make all your changes. Ribbon updates can be done in a minute or two without the hassle of dealing with the XML by hand.
Jason Lattimer
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