This is what I too was referencing. How can it be accessed via KM?
I am confused, though, because while I thought this Shortcut was new in Monterey, it shows in Finder as a Quick Action, and they have been around for awhile (apparently — I never knew they existed before). IOW, it's a new Quick Action, not a new Shortcut, afaict.
I had no idea you meant "Monterey Shortcuts" because (a) you didn't say that, and (b) you mentioned "four output sizes" and that's not what Monterey Shortcuts offers in its Convert Image action. So naturally I thought you were talking about something else, which I probably assumed was Automator, which also uses the term "Quick Actions".
When you said, "How can it be accessed via KM," are you talking about Monterey Shortcuts? If so, they can be accessed via the "Execute Shell Script" action using the macOS command "shortcuts run name-of-shortcut". There are about eight different ways to access Monterey Shortcuts, but I presume that's what you are asking about.
I remain confused — are there different "Convert Image" utilities? I am seeing four image size options when in Finder I bring up a context-sensitive menu with an image file selected and execute "Quick Actions ▹ Convert Image". They show like this when I click the drop-down icon to the right of the "Image Size" field:
In the Shortcuts program on my machine there are only 6 Shortcuts and none are named "Convert Image" or anything like that. When I try to run a Shortcut named "Convert Image" using either the KM Action "Execute AppleScript" or "Execute Shell Script" I get, unsurprisingly, either an error or nothing happens.
You would need to build your own OS Shortcut, looking something like this and then call that OS Shortcut from Keyboard Maestro using the method @Sleepy has suggested.
To call this OS Shortcut from Keyboard Maestro you would use an Action like this:
In the above example I made an OS Shortcut and called it "ConvertImageJpeg".
OS Shortcuts are similar to Keyboard Maestro Macros in that they are formed from blocks that you put one after the other, a bit like Keyboard Maestro Actions.
What you showed is definitely not Monterey's Shortcut's Convert Image action. I have plain macOS Monterey. I'm guessing that you installed something that gives you that "Quick Action." So when you said "That is what I too was referencing," I don't see that as being correct. @Zabobon 's post may clarify it for you.
So going back to my original comments, when I said, "I don't think anyone mentioned that Monterey macOS has new built-in image conversion through an action in shortcuts which you can access from KM," I think that comment still stands as a fresh new idea.
Incase anyone needs this, I edited the macro so it converts a heic file airdropped from iphone to downloads on Mac, then converts it to jpg and deletes the heic file