How do you set that to run on auto-run when the OS starts? Or in general, when Chrome is launched in some other way than you typing that on the command-line?
At least on Windows, you should be able to modify the target property of the program’s shortcut to add any desired flags. Then use that shortcut to launch, or drop it in the startup folder.
On Linux idk, maybe an alias?
What shortcut though? Auto-launch is automatically set by Chrome in the registry, and Chrome really doesn't like you to mess with things it manages in general, and would eventually overwrite this in any case. Also I _think_ messing with shortcuts sometimes has weird effects with Chrome, like on taskbar grouping, though it's been a while since I've tried.
In Windows, at least, you can make a batch file to launch Chrome with that option, and then use a shortcut to that batch file to open Chrome.
You can skip the batch file and just include the flag in the shortcut.