LAD is the first step. Previously, controllers were only discrete data. The task of the LAD to draw a logical (And sequential chains, OR parallel). Added more timers and counters.
Then came the FBD is the same chain, but to handle integers and floating point numbers. (Operations And and OR steel blocks).
Finally, the CFC: first, instead of just a bunch of chains all drawn on one sheet, and secondly, the possible feedback.
If you want to learn programming, you probably need some manuals on the schematic.
I advise you not to miss another two languages. Text ST - will help those who wrote the regular program. We just need to remember that any program should run from start to finish during the scan.
And finally, what I like - SFC, or state graph: allows you to graphically break the task into several pieces, each of which can be programmed in any language. Examples of "control logic"
can look at "an exponential rate" (representative of MatLab in Russia). However, I doubt that you buy MatLab, but it will help you to master in the future SFC (in Matlab this is called Stateflow and drawn a bit differently).
Try to search manual on Codesys.
For beginners, I came across a playlist of Andrei Kulagin