To change the contents of a message box, use the 'set' message

You could write the values via a sinesum message to an array

Another way when patches disappear off screen on windows 10, is to hover over the Pd icon on the task bar and right click on the missing patch's large icon title bar then click maximize, then drag down the maximized title bar to restore its size.
The missing patch appears as a blank patch on the task bar icon.

I think [list split] is what you need

Another possible choice is to use [makenote] instead of [pipe], although 1 millisecond needed to be added to the bang delay.
chord-loop.pd

@esaruoho I sent this while you were replying and might of skipped it

the bang between [r $1-id] and [array get plom$1] looks like it is blocking the id, and the delay is toggling the metro twice

the bang between [r $1-id] and [array get plom$1] looks like it is blocking the id, and the delay is toggling the metro twice

are all the arrays the same size?

Did you close the edit window with the "done" bang?
If not the metro will still keep updating the last array that opened it.