The GridBrushBase class has methods that you can override to handle changes in Z position. This allows you to have custom behaviours for your customised Scriptables Brushes. These methods are:
public virtual void ChangeZPosition(int change):
Changes the Z Position of the Brush. The change argument is the amount that is changed by using the Hotkeys or the Z Position Inspector.
public virtual void ResetZPosition():
Resets the Z Position of the Brush. You define what value to reset the Z Position to.