Actually since 1.4.2 this can be written with our programming language. Trick is using
@sendToPrinter slug command
Sends command to the printer with given slug name. That way you can execute command sin the context of another printer. Note that command and all command parameter get parsed first in your printer context, so outer quotes get removed and computed expressions get executed. Escape them if that is not wanted accordingly.
So lets say you have printers with slug names a, b and c and a ist master server, you can write a function
@func all cmd
@sendToPrinter a {{local.cmd}}
@sendToPrinter b {{local.cmd}}
@sendToPrinter c {{local.cmd}}
@endfunc
Put this in event dependent activate script, deactivate and activate so it gets run. On restart of server it start automatically if printer is activated.
Now you can run
@call all G28
to home all 3 printers.
You can also make a own dialog with most often used parallel commands to be lazy.