Sure, it clearly says, "signed by President Buchanan", and Lincoln forwarded it.
If that's your whole case for Lincoln "orchestrating" Corwin, then it's ludicrous.
Forwarding is hardly "orchestrating".
I'll repeat, if Lincoln "orchestrated" anything, it was the defeat of Corwin, since only a handful of states ratified it, and most later rescinded.
Indeed, if you truly want to blame somebody for Corwin, then that should be Senator Jefferson Davis who submitted his very similar version two months before Corwin did.
That's where it got started, not with Lincoln!