Oh look another feature!
(Solved!) Actually the problem linked to above - corrupt jwm config file preventing config modification under JWM Configuration GUI - wasn't "solved" per se. Instead I discovered that manual modification of ~/.jwm/jwmrc-theme as per JWM's creator and the ArchLinux Wiki is fun and easy and affords far greater customization possibilities. So all I did was turn my lemons into lemonade! Cheers!