Returns a list with the number(s) of the macro(s) matching the given name. If no macro with that name is found, returns an empty list. If there are several macros with the same name, returns the numbers of all of them.

The number of a macro is necessary to edit it. However, as the user can change the order of macros, create new ones and delete old macros, a macro's number may change, so you should not store its number; you must fetch the number just before editing it.