Where to put unused neutral wire for light switch

[Ricyteach]

Howdy DIY soldiers, first post here.

My question comes down to whether it would be particularly unsafe for me to temporarily wire nut and tape a neutral wire connected to an active knob and tube circuit and leave it in a wall behind a plastic box.

I know that the "correct" answer per the NEC would be for it to be left inside a box. But the wire is short enough that I can't get it inside the new work box. In order to get it inside a box in the wall cavity I would need to rip open my plaster and lath wall to get a box in there to leave the wire inside a box. I do not want to do that. I do not have time right now to rip open a bigger hole and then repair it.

Maybe there's a product made for this kind of situation? I can reach my hand inside the hole in the wall cavity, it's a two gang box hole that already existed. Maybe there's a nice product that I can tuck this wire inside of and reach into the wall and maybe easily fasten it to the stud? But likely not since there's just not enough room for me to get my drill or a hammer in there to fasten.

I am running new wiring to light switches in that wall. The old switches are switched on the neutral wire, and the neutral wire that I'm talking about leaving in the wall disappears into the next wall cavity where it connects to the main neutral wire for the circuit.

I'm temporarily going to continue to use that existing k&t circuit in this wall (coming from my basement to my attic). In the next couple years as I get my attic remodeled, I will abandon that knob and tube circuit entirely and wire this circuit to the breaker box in the attic. So this neutral wire inside the wall would only be connected to an active circuit for a couple years at the most, after which it will just be a dormant wire.

Just FYI: I do have a lot of experience doing electrical work in old houses, but this is a situation I haven't had to run into before.

 

[littlespark]

Things are obviously a little different in UK, but situations like this, we would put a connector on the end, then enclose it in a box… even within drywall.
We wouldn’t have unprotected single cable within a drywall anyway. Would be sheathed, or within conduit entering the box.

Can the wire be disconnected from the main neutral at another point?

 

[Ricyteach]

It could be disconnected, but the place it connects to the main circuit is inside the neighboring wall cavity and so it would be a similar problem: a lath and plaster mess.

Your response reinforces what I know is the correct thing to do: put it in a box. But the only way I know to do that is going to require a large amount of effort. I'm still inclined not to do it.