Indicating the charge level on a capacitor with an LED
I need to make sure that the capacitor is completely deenergized.


The way you make sure a high voltage capacitor is completely safe before working on it is to have a wire connecting both terminals together. Clip a wire onto both terminals. Use a conventional multimeter, with a HV probe if necessary, to see whether it's safe to attach the wire.

An indicator LED system is prone to all sorts of failure. If the light is off, then is that because the cap is at a safe voltage, or is it because the light has failed? Are you feeling lucky?