Currently, if autoupdate is disabled, it's possible to trigger an update within the UI.
I believe this is also achievable via the newly announced OneAgent API (but I did not try it yet, but it looks like the autoupdate configuration allows you to set the version you would like to update to):
As Julius mentioned, the API is certainly an option to change the behavior of individual OneAgent updates on specific hosts. But this only changes whether the OneAgent AutoUpdates are Automatic, Manual, or Inherited.
This does not force an update at the moment of the API call. So i'm still abit unclear on the original question. Hope this helps.
@Morsi T. Take a look at the links provided by Julius earlier in this thread. He provided the link to the API doc describing how to specify update parameters for a specific host (or group of hosts). But be aware that while you can specify the upgrade version for specific hosts, it's not necessarily going to update the agent at the exact moment of the API call. I don't believe there's any contract stating how quickly the update will happen.