I just noticed that Cmd-A is used for “Save As…” in module editor mode.
MacOS apps would use Shift-Cmd-S for this function (e.g. see Mail). Windows, apparently, uses F12.
To avoid conflict with modules, fewer control keys used by the top level window command bar is better, especially ones that whose “reserved” use is not so well-known. There is a more troublesome MacOs conflict, affecting normal module users under v3.3.3 that I will log separately.
Mark