When you disconnect equipment, the main concern usually should be for anything that's still powered on (or carrying a charge from being on until a few moments ago). As an extreme example, think of a public address system that's turned on, and you disconnect the microphone. If the mike cable is still connected to the amplifier and speakers, this can produce a very loud "pop" or "bang" that could blow out speaker drivers and/or power amps. People standing near the speakers could spill their drinks on their partners, leading to nasty break-up scenes and eventually child custody battles and so on.
Disconnecting a condenser microphone capsule from its amplifier (the mike body, active cable, and/or outboard preamp such as your Nbox) is no threat to the capsule. But if the amplifier is on at the time, it will receive a voltage spike which it will try to amplify, and so on down the line. Most of the time that will be completely harmless, but there may be that one time out of 100, so it's not recommended.
I mean, at trade shows, I've seen Schoeps engineers unscrew the capsule from a microphone and replace it with another capsule, while the mike was powered up and connected to a preamp and headphones. They turned down the preamp gain temporarily, but the preamp's input circuit and the phantom powering were on the whole time. As I said, most of the time that will be completely harmless--but then again, those engineers had replacement mikes available if anything went wrong ... which they claimed it never did, but they still don't recommend that practice to customers.
--best regards