Nobody assembles the kit deliberately. It accumulates — a way of speaking to an official that you learned from watching your mother, a trick for getting started that you stole from a colleague in 2016, the knowledge of exactly which friend to ring for which category of problem.
You would struggle to write the inventory out. That is normal; most competence is stored as instinct rather than as a list.
It tends to appear when required, which is disconcerting and also the point. You find out what you have while using it.