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I would love to know the answer to this as well. It doesn't seem possible to simply copy and paste a property value.
And to be clear, I'm talking about GEOMETRIC properties such as SCALE and POSITION which are not covered by MATCHPROP, as far as I can tell.
On Linux selection by mouse, then middle click to paste may work as an alternative.
On Mac cmd+C/V also does not work but right click or control click does work to show a context menu that contains copy.
We noted this bug internally (apparently it has been broken all along and this bug slipped our attention).