With some simple math I can smoothly transition from square (odd harmonics) to saw (all harmonics) to even (even harmonics + fundamental).
VCO Lab Morph Square-Saw-Even.vcv (3.8 KB)
Now I am thinking that if I add the even waveform to VCO Unit (or maybe VCO Lab), I will simply add an additional shape mode to the saw waveform to do this transition. Fully counterclockwise would be square. Noon (no modulation) would be saw. And fully clockwise would be even.