I think that if I configure the Behringer Neutron's assignable output to the oscillator 2 control voltage, I can turn the oscillator 2 tuning knob and emit from the Neutron's patch bay a constant, manually controlled CV. (Page 13 in the manual.) This seems like a straightforward way to control something in a modular system that has a CV control but no knob.

(By the way, this isn't a great sacrifice, because I often don't like the sound of the Neutron's two oscillators working together in sync, and I think it's because of the issue described in this YouTube video of a modification performed to correct the issue: )