Thanks NR, not a huge priority or feature request. There are other more amazing things that would provide the Sunvoxers with more musical inspiration than my observation. I found a way around it anyway. I just enter the same key to cover up the second entry in the list, seems to work fine.
I have now successfully mapped all three octaves on the qwerty to a harmonic table with C-0 on the '>' key. Minor thirds are horizontally to the left, major thirds are the key right hand key diagonally above the root note and perfect 5th are above diagonally to the left. This allows minor chords to be constructed with a triad of three keys making a triangle pointing down and major chords to be constructed with a triad of keys pointing up.
Essentially low notes are in the bottom right hand corner of the keyboard working toward higher register notes in the upper left. Minor thirds run horizontally right to left. An alternative arrangement would be to map it so major thirds run from left to right horizontally, low notes in lower left, high notes in upper right. Basic chord shapes would be the opposite of what I previously described.
I'll post something on the Facebook Sunvox page to demonstrate.