notification actions with variables not working (macOS)

[benzoo]

I've noticed, that usage of variables in notification actions strings are not working. For example, I've tried with simple action string "touch /tmp/$HOST$" or "say $HOST$" and what I got was /tmp/$ file in fist case and "dollar" voice. Could this be a bug? I'm using Nagstamon v 3.0.2 on macOS 10.13.3.

P.S. in Action string under Custom notification action, $EVENTS$ variable actually is working, but only this one?