Phil,
You can do this from the front panel by selecting the "Key -> V/U" buttons. I have an FTV-901R that's been modified by Yaesu to work with the '980 and IIRC it toggles those lines as its band switch is moved. (Would hook them up and try an experiment but the transverter is stored away at the moment).
The FT-980 Technical Supplement provides info on which lines are used with a transverter for frequency display. I'd given some thought to rewriting the firmware and adding our 222 and 902MHz allocations to the available selections if space permits.
73 - Fred, N8YX
