What is the easiest way to modify these pivot tables? I assume it must be easy to add new investigators or have it automatically find them.

I definitely need to study up on Pivot Tables as they appear to be a very powerful tool.

New investigators will be added as you enter records in the log for them. If you want to use the data validation drop downs, you first have to update the investigator's list on the Data tab which is easy enough. Then add records to the log. Lastly, you need to refresh the pivot after any new data is added. Right click anywhere in the pivot and select Refresh.

Don't be intimidated. They are really easy. Just play around with them and you'll get the hang of it.

Look over what I posted and let's talk about next steps.