1) Start with a 2 piece drill sleeve; [those slick packages for new cutting tools] large enough for connector attached to vehicle side
2) Slot female side to accept 4 or 7 wire bundle.
3) Insert free [un-spliced] end up through tube and out the slot.
4) Retract connector inside female side and insert male; this combination resists dirt surprisingly well.
Some tubes aren't injection molded, but roto-molded; they have some taper and fit too loosely after sectioning. So the twist lock feature can work, I bonded 1/3rd of the section removed to male side, opposite of the locking lugs. That was sufficient for them to engage.
5) With a pair of tubes, make a duplicate male for the trailer side, handily encasing the whole shebang.
6) The same idea works with plastic prescription containers......
Would have been my tag; "Trailering, 12v Electrical Housing, Shameless jab at YT vids; where decent text suffices..."