There was a wide selection of helper functions that just disappeared in R2019b that were in R2018a. Do you have anything that can help identify if these functions still exist, name changes if any and where they functions went?
I believe the examples were reorganized at some point in the last few releases so that helper functions (which are specific to the examples) are no longer on the MATLAB path by default but are still accessible to the examples.
If you open an example that has hyperlinks to the helper functions at the end (like the 802.11ax Parameterization for Waveform Generation and Simulation example) as a Live Script clicking the links will open the helper functions. Alternately if you open that example in the Editor using the command openExample('wlan/HEParameterizationExample') the directory that contains the main example file should (at least it does for this example) contain the helper functions.