I think step one is setting up a systems model for various neuron types, the cortical column and wider systems. I’ve set up a thread to discuss this here: Systems Diagram and understanding of the Neo Cortex Mark Browne offered some great links to work done on systems understanding there starting with this one: http://www.mrc.uidaho.edu/~rwells/techdocs/Cortical%20Neurons%20and%20Circuits.pdf. The goal is to have a fully integrated systems approach to organize the effort.
Interesting work in the role of dendrites in parallel processing: https://actu.epfl.ch/news/the-way-a-single-neuron-processes-information-is-2/