Updating the bend editing graph to bend a note down from original pitch too?

So far, I can only easily bend a note upward or bending the note up/down with any tones at/above the original note pitch, but I can't go anywhere down from the original pitch by moving the nodes in the bend editing graph. The nodes' lowest positions represent the original note pitch and cannot go any lower. Can the bend editing graph get an equal capability of creating bends in the opposite direction of what is possible now, using lower tones? Having the original pitch be the center line of the graph instead would be much better than being the bottom line, so down bends from original pitch can be possible this way.