VKB-SIM

It seems the the drop down doesn't get saved and as a result you can only bind scroll up.

When going back to that button the main drop down for the mouse section is blank and it's back on buttons from scroll wheel mode.

Not enough information

If you use a logical button for scroll, you need to dial in a non-zero number of steps to be able to choose a direction

Thanks, I see
Try VKBDevCfg-C_v0.93.18

Yep, that version fixes it.