The adverbial pronoun en is sometimes placed after ne instead of que:
à n'en savoir que faire
With this word-order, the pronoun que is sometimes replaced with quoi:
à n'en savoir quoi faire
Though savoir is one of the few French verbs that does not necessarily require the use of pas along with ne to be negated, it is quite common for it to be included in this locution:
à ne pas savoir qu'en faire.
Similarly, the quasi-negative element plus is often added, with our without the shifting of en mentioned above: