Could be great to be able to add some IPs to an existing Alias or some domain name to a proxy/webblocker rule using API in order to feed a kind of "Black List rules" from a CTI tool for example.
You can add sites to the blocked sites list via the CLI, or import using WSM's policy manager.
If it's a cloud managed device, I'd suggest looking into WG APIhttps://www.watchguard.com/help/docs/api/Content/en-US/home.html
WatchGuard Customer Support
Great for the future ! but not yet "Cloud managed" device here ;-((