You are correct: I don't KNOW whether or not the docs exist. I do know that getting them is difficult. I've also seen the spaghetti wiring that is done. That is more what I am commenting on. I also believe, based on experience, that even if you have the docs your "as built" scenario is likely somewhat different anyway, especially as it relates to wire routing and that is more what you need than what circuit is on what fuse/breaker. If the panel is labeled correctly you have that info. How the wire gets there you don't have.
But we have digressed. The original intent is to split an outlet to another circuit to avoid blowing a breaker. That will involve either putting in another outlet wired to another breaker, or rewiring an existing outlet to another circuit. In either event one needs to know where the wires are. If it were me, and there is room in the converter for another breaker and I can figure away to install and wire another outlet, that's the route I would take. Unless I can easily see the wire run to an outlet on another circuit that I can easily tap into. And I'm thinking that's hard...
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