Maybe I am having another senior moment, but I think you have to remove the underscore from the macro name to use it in setaccel.
setaccel("MButton","macros(_DuplicateTab_Focus)");
should be
setaccel("MButton","macros(DuplicateTab_Focus)");
and corresponding change in
DuplicateTab_Focus{
That's the way I tried it, but it still did not work.
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Bugs