The basic halacha is that he shouldn’t even sit on your bed in your presence when you are in niddah, and may not lie on it even when you are not present. Therefore, unless there is great urgency, he should not plug things in when you are in niddah if doing so entails lying on your bed.
You might consider using an extension cord or a smart-plug (controlled by your phones) when you are in niddah, so that he still has access to the outlet. Alternatively, you might consider switching beds, since a wife is permitted to lie down on her husband’s bed in his absence.
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