I'm having an issue with this. I've fixed it, but consider adding this to your system.
When I hide/disable the dash bar using the Switch, then re-enable it, it doesn't show the window until I enter and exit another scene, such as scene menu or scene save.
This can be a big problem when trying to enable and disable the bar to keep it from becoming intrusive.
To fix this, I change Window_Stamina's method
def update
and find the line
self.hide if !$game_switches[YES:

ASH:

ISABLE_SWITCH]
and replace it with:
!$game_switches[YES:

ASH:

ISABLE_SWITCH] ? self.hide : self.show
Also how about implementing something like this:
#-------------------------------------------------------------------------- # new method: adjust stamina #-------------------------------------------------------------------------- def adj_stamina(value) @stamina += value end
Though, if it was my UI I'd make adjusting that variable a lot easier and accessible for non-scripters.