This is simplified description:

I have created a plugin and it's functions are under new menu named "bgTransform".

It opens by default with "Alt+b", event when I don't put ampersand in front of it. So these entries in source code both work:

bgTransform / f1
&bgTransform / f2

However I would like to have another menu named "fTransform" and access it with "Alt+z" ( since "Alt+f" opens file menu by default ).

Can it be done somehow ?