Project Launcher Custom "Post Build Event"

This feature would appear in the left “Launcher” tab you have shown as the first image on those docs.

I’d like to have a “custom” step after deploy, or even after Launch, at the end of the Project Launcher package toolchain.

Cook->Package->Deploy->Custom->Launch (The Package step is present in earlier/different UIs)

The Visual equivalent to this is called Post Build Event, which allows you to run an arbitrary command after an engine compile (i.e. update a web script / call a Jenkins job / etc)

Hopefully that makes more sense. However the automation testing docs are quite interesting.