Which version of photoshop and mac os x are you using?
Shift + F5 or Shift + Delete doesn't bring up the Edit>Fill dialog?
I don't think the Caps Lock key can be assigned as a keyboard shortcut in photoshop.
WOOHOO! shift + delete works! Thank you!
I'm using photoshop 2014.2.0 & I'm on a macbook air 10.8.5 mountain lion.
When I go to the 'edit' tab, it indicates the hotkey for 'fill' with an upward arrow followed by 'f5'
When I tried that, it changed my display brightness settings.