@SimonPepinLehalleur As Edoardo said, a lot of this stuff was already developed for complicial sets, and the recent work of Gagna-Harpaz-Lanari more or less gives you a way to apply this in concert with Lurie's (un)straightening theorem by completing the equivalence between 2-trivial complicial sets and scaled simplicial sets
However, Yuki's paper is also excellent and has a bunch of interesting (∞,2)-categorical combinatorics. I personally prefer the Θ-type models to complicial sets, mainly because the representable objects are all fibrant and represent the obvious elementary operations of n-category theory. I was very excited to see this come out, but Gagna-Harpaz-Lanari does give you, at least right now, a better toolbox.