Search through multiple Categories for common parameters

I am slightly frustrated at my current workflow in acquiring lists of parameters from elements of multiple categories.

I have been looking for a way to query groups of Category’s elements and capture the parameters from them. Until now I have been trying many different directions. The firs was to build a node that queried the elements based on the input of the Category type.

This had to be multiplied many times to acquire all of the results.

I have also resorted to some Python scripts for selecting multiple categories. I am pushing my limit. Has anyone found a way to select multiple categories and query them at the same time?

Hello.
Is the custom node not working when you input a list of lists? Can you show us the outcome and what you wish the outcome to look like?