I set fn-Q as CAPS LOCK and quickly realized that there’s no status LED for that.
I see that there’s a caps lock plugin which turns the letter keys red, but I’d prefer not to mess with my shift keys.
There’s no requirement in the CapsLock plugin that you bind it to fn-shift, so you could bind Key_CapsLock to fn-Q and get the same effect while leaving the behavior of fn-shift alone.
As for monitoring the state of LED_CAPS_LOCK (which, in theory, would be the thing you’d use to control the light yourself) I found that once it’s set to true it’s never set to false again. I don’t know if that’s a bug or if the keyboard just expects a different key sequence to toggle it back off, but it didn’t disable on a second press of Key_CapsLock and it didn’t disable on a press of either shift key, and I didn’t know what else to try. The plugin gets its initial state by looking at LED_CAPS_LOCK, but after initialization it tracks its own state.