Set mod buss 2’s source as filter EG and then press and hold buss 2’s destination button and turn mod buss 1’s pitch knob. This will assign buss 2’s assignable destination to buss 1’s pitch amount.
Now use buss 2’s assignable knob to dial in the amount of filter EG signal controlling the pitch knob of buss 1. (Leave buss 1’s pitch knob flat unless you want a base FM amount in the sound.)