Arlington NM844 Connector

Appears to be a cable clamp that allows 10 10/2 wires to be bundled through a single knockout. https://docs.google.com/presentation/d/1qzTNV2n-UMCY6J5qQG_geLeMq_7ycntecO-R-snSdx0/edit#slide=id.g22d737843bb_0_0

$1.37. [1]

The 'common answer' is that only 2 wires can go through a single knockout. Google it.

Chase Nipples. are another long discussion and a potential solution. For simplicity, a large inward-facing cable clamp or chase nipple going into the wall from a surface-mounted cavity could work.