OK, I found it. It does look to be brazed to the shaft, but I think a copy of the front clamp-on lever would also work.
I've fought problems with returning to the set idle myself, found issues all the way from the nylon bushings in the firewall binding when they get hot, to wear in the bellcrank pivot allowing it to drag on the bolt head, to wear in the linkage pivot balls causing them to bind only at idle.
But the most common, for me anyway, is wear in the front shaft bearing/bushing allowing the throttle plate to drag on the bottom of the bore. That has been my main motivation for rebushing carb bodies twice now, and both times it made the problem disappear.