I'm currently trialing the Mac version of Goodtask. Something seems to be wrong with the URL scheme: links such as goodtask3://add?title=Title&list=to don't do anything (if clicked from another app, e.g. Obsidian). The Goodtask shortcuts in the Shortcuts app also don't work.
Trying to access the API using x-callback results in the following error: "Shortcuts could not open the app for the URL scheme “goodtask3” because the app is not installed on this device".
So all in all it seems the Goodtask URL scheme isn't available for one reason or another.
I'm on the latest Goodtask, on Monterey with an M2 Macbook Air.