The list of all layers that we are currently working on and plan to produce are in the pdg-portal repo. Each "layer" issue has notes on the location of the data and any processing that has been completed thus far. The way we keep track of the highest priority ones is through the PDG project board here. The P0 datasets should be processed first, followed by P1, P2, etc. Blockers for datasets may be described in the tickets.
There are also some layers listed in these slides created at the beginning of the project.