Simon 5 is coming soon!
Simon version 5 is currently in beta testing. It is a massive update, introducing a much-requested feature: syncing the Simon data between multiple Macs, plus a Simon Status service, a Link Checker filter, improved Find filter, iMessage and Speak Error notifiers, a new app icon, and much more.
Important: please note that Simon 5 requires a minimum of macOS 10.12 (Sierra), and will be a paid upgrade from Simon 4 after the beta. Purchasers since September 1, 2020 automatically get a version 5 license (that also works in previous versions).
Re: Reword Filter Response
In theory I could add support for variables in the Not Found field. However, that wouldn't help this situation, as the text the filter is searching for isn't available as a variable. I'm not sure how feasible it'd be to make it available; I'd have to research that.
It's a good idea, though.