It's worth noting, I suppose, that once one gets past the commercial pilot certificate and basic multi-engine, most checkrides thereafter, for most people, are instrument checkrides.

The commercial pilot practical test is a redux of the private with a little more added on.

The airline transport pilot (ATP) practical test is an instrument rating checkride to slightly tighter tolerances

Everything thereafter; each line check, proficiency training, type rating, and so forth, is done to ATP practical test standards, and is really more of the same, tested over and over.

As noted above, when you get to the point of seeking ratings for specific airplanes (type ratings), the process turns into a 1-2 month deep-dive into every little detail about that type of airplane, how it works normally, how it is operated when things don't work normally, and how to do both to ATP practical standards, including all the same stuff you've been doing since your initial primary training...stalls and steep turns, and so on. You'll do all the stuff you're working on with your instrument rating: holds, arrivals, departures, instrument approaches with all engines, and instrument approaches with an engine shut down. Engine failures on takeoff, rejected takeoffs, and so forth. You'll do the big-airplane version of "partial panel" with various malfunctions such as loss of airspeed or different electrical problems, and deal with some of the more complex systems like cargo fires, and so on...but always while operating the airplane to ATP standards...which are mostly instrument rating standards, tightened up just a little bit. Lots of study.