It seems that Apple is working on a full-fledged port of Siri Messaging and Team applications from iOS to Mac. Evidence for this was found by developer Steve Troughton-Smith.
This is possible thanks to the Project Catalyst project, in which the company creates cross-platform applications for iOS and macOS. As follows:
iMessage Effects! pic.twitter.com/e6VM0xa6g4— Steve Troughton-Smith (@stroughtonsmith) June 19, 2019
And, just for reference: this isn't a 'marzipanified' version of the Messages app from the iOS Simulator. This is the 'native' Catalyst UI coming from the macOS 10.15 system frameworks. Just like Shortcuts, it's all there, and mostly works if you know how to talk to it pic.twitter.com/VO59kPbbVY— Steve Troughton-Smith (@stroughtonsmith) June 19, 2019
Surprisingly, even effects can be applied to sent messages.
Curiously, the company did not mention Siri Commands and Messages during the demonstration of the first applications on macOS Catalina. So it is entirely possible that they will appear in later builds of the operating system. [ MacRumors ]