Where can I find documentation about controlling the simulator programmatically?

I don't think that info is public or will be made public.

That would be very disappointing. Any idea why?

I suspect it's different things

1) The interface was built for the app settings editor in eclipse and not for a user's app and might be subject to change.

2) documentation and maintenance - available people.  This is the first time I've seen a request such as yours since app setting was introduced in 2016.

3) There's probably been few issues with the app settings issues from eclipse, and you can run through a number of cases fairly quickly with it.

App settings when using VS Code is something Garmin is working on, and one of the reasons the VS Code extension is not yet "feature compatible" with Eclipse.

A few people have asked about programmatically controlling the simulator and/or auto-generating app settings in the forums.

For auto-generating app settings (without modifying your app), I suggested reverse-engineering the .SET file format and generating SET files programmatically. Once you do that, you can copy the .SET file to the simulator directory (in the %TEMP%\GARMIN folder) and restart the simulator using the command line. (Of course this only works if you don't mind restarting the app.)

The person who asked the question about auto-generating app settings came up with a much simpler solution: they auto-generated app properties file with the settings they wanted, rebuilt the app and restarted the simulator.

If you really want to see how the app settings editor communicates with the simulator, you can use Wireshark and try to reverse-engineer the protocol. But then of course you also need a way to auto-generate SET files, unless you script the GUI of the app settings editor.

Yeah, wiresharking is what I was contemplating doing.

Rebuilding/relaunching could work, but I was hoping to also control things like the time displayed.

For watch faces, the sim has time simulation.  It's useful if you want to do something like insure the time "fits" for a full day in a short amount of time.  There's also the heat map if you want to run a test that spans a bunch of time to check on burnin protection for venu/venu sq/venu 2 devices.

I'm aware. I want to automate these things.

I also wanted that feature, but I didn't have it, so I created a scripting feature for my watchface test and help screen captures.
The operating environment is Windows10 + PowerShell7.

The software itself is C # and is published as a Nuget package.
The operation script of the simulator is configured to be assembled with PowerShell.

It uses the Windows API, so it probably won't work on Linux or Mac.

help
take4-blue.com/.../

Source
github.com/.../AutomationConnectIQ

How to use API etc.
take4-blue.com/.../

A video capture of what is moving.
take4-blue.com/.../