>> Usually context menus on file managers include two items:
>>
>>   "Open" that opens immediately
>>   "Open With" with a list of commands
>>
>> So "start" will be used for "Open With" if someone prefers this.
>> Then a new command 'dired-do-open' bound to the "Open" menu item
>> will hard-code 'w32-shell-execute' call with the "open" command.
>
> SGTM, thanks.

Here is this new command 'dired-do-open':