Well that's funny. After a couple of weeks, and dozens of boots, I've suddenly got the icon back in the status notifier plugin. So I can click Preferences.
The icon still doesn't go grey / black with capslock on / off, but a reasonable workaround is unticking Show indicator while capslock is inactive. That lets the icon appear / disappear appropriately.
Well that's funny. After a couple of weeks, and dozens of boots, I've suddenly got the icon back in the status notifier plugin. So I can click Preferences.
The icon still doesn't go grey / black with capslock on / off, but a reasonable workaround is unticking Show indicator while capslock is inactive. That lets the icon appear / disappear appropriately.
So I guess, Solved, kind of.
Either way, thanks for this neat little utility.