this is sort of like saying "I have a good understanding of wheels and balance since I can ride a bike, so now I want to design a jet airliner".
there are LOTS of theory of electronics and electricity that is particular to motive traction motors (a motor becomes a generator as soon as it is being driven, and not driving, as example) and forklift operation, and hydraulics before really being able to get the average person's head into the operations and functions of any electric forklift's control systems.
A solid understanding of motors and generators, then into semiconductors, then explaining the operation of field effect transistors, and a solid knowledge of forklift physics would be prerequisite to 'just jumping into the 123 modules' operational understanding, in my not too humble opinion.