It’s inside of an Editor Utility Widget so it can be docked in the viewport where needed.
You can also access OCIO from the viewport
Note:
You can only access “Set Active Viewport Configuration” from within Editor Utility Widgets. The node doesn’t show up in normal game blueprints (actor, pawn, character etc)
If you want to trigger it in game then this might work: (though not tested in packed)
config
You could also use c++ do to this but it would be overkill.