The downloaded Mach3 instructions say:

    The Operator>Macros menu item displays a dialog which allows you to see the currently
    installed macros, to Load, Edit and Save or Save As the text.

But I find no such menu item under Operator.
Where can I learn about macros, how to use them, and how to write them?

I think what the manual may be referring to is VB Script editor and also Edit Button Script. Both of these will allow you to open VB or VB buttons and view or edit a macro or button script.

There is no where really at the moment that has info on writing macros apart from some snippets in the customising Mach2 manual and I think also some info on the Wiki.

Ray is writing a VB manual for the next revision of Mach but at the moment the best way is just to look at macros and buttons and see if you can work out whats what. Also you can look at the VB buttons in the wizards to see how they have been done, just dont look at the Write wizard unless you are a guru in VB
Hood