Chris - you nailed it. A folder for the actual certs, and a spreadsheet.
I made my own spreadsheet, which includes the date of the PDH, the providing organization (ASCE, GI, local vendors, etc.), the title of the presentation, the presenter, and the number of PDH's acquired. I have a monthly calendar invite that reminds me to check my calendar for any scheduled trainings, scan/download and PDH forms, and update my log. This has been very useful when I have been audited on my PDHs - save the relevant time period from the log, combine the proper time period of PDHs (hint - add the date in the title - 20210824 ASCE etc.), and send to the appropriate state board.
If you are tracking PDH's, you are an engineer - have clear, linear, thought-out process.