I use Excel spreadsheets to plan all of my trips. I track between each stop Drive Time, Miles, Arrive Time and Time at Stop. I then sum up the entire day to make sure I don't bite off more than I can chew. I've used this for all of my courthouse planning and expanded into any just random drives where my time at stop might be zero. I then print the spreadsheet to have in the car to track how far behind I'm running (I always run across something cool or unexpected that puts me behind schedule!). I should add I also use Atlas Obscura, Roadtrippers and a review of the National Historic Register by county on Wikipedia to find interesting sites in addition to my focus on courthouses. I'll list these on spreadsheet too with address and hours.
I should mention my background is accounting and finance, so Excel is my go to for everything. ;-) It's useful though as I have a record of all my past trips. During pandemic, I laid out a huge spreadsheet of future trips with rough routes to visit all courthouses in all the southeastern states (finished GA last year, but mapped out AL, SC, NC, TN, and MS into several 4-5 day trips each). Plan is to slowly chip away at my list now.