Merging without nasalisation

The mechanic

Before ل or ر at the start of the next word, the noon or tanween disappears entirely into that letter, which takes a shadda, and no nasal sound is held.

Where it occurs

The two letters this idgham folds into

ل ر

A place in the text

وَلَمۡ يَكُن لَّهُۥ كُفُوًا أَحَدُۢ

The marked spot was located in this ayah's own text at build time — Al-Ikhlas 112:4.