Glad to hear you are enjoying the update. The H90 manual doesn’t mention this because its a brand new feature exclusive to the H9000!
The MIDI note control will change the shift amount in increments of 100c relative to the middle C position, and the MIDI monitor will reflect these changes. So, middle C will not shift by any amount, C# will shift by +100, D +200, and B below middle will give -100. The idea is that you set the shift amount from the main voice parameters, and then offset those shifts by sending MIDI note data. I’ll post a link to the updated H9000 documentation when it is available.