I'm glad to see that you're pleased with your cook. That's a big hurdle. Now you're well on your way for tweaking, experimenting, and just plain having fun at the pit.
BTW, for now I have a note pad that I jot down the following info.
Date, cut of meat, where purchased, price per lb, total weight and total cost.
Next, note how the meat was prepared for the pit. For example, note the rub you used.
When the cook starts, make notes such as start time, weather conditions (If applicabale) and anything else that may be a factor.
During the cook, everytime you check the pit, note the meat internal temp and other factors such as grate temp, lid temp, etc. as you go along. I usually note when I dump ashes, and when I load more fuel.
At the end, note finish time, final prep methods and yield. Add any other comments such as "needs more salt", "too much salt in rub", etc.
Print copies of pix, if any. Put those and the notepad notes in a top loading sheet protector.
One day I may work up a word processing form with blocks for these items and print out a bunch of blank copies, but for now, the notepad works fine. Tried going from raw notes into a word process doc but that turned out to be too much trouble. (For me, at any rate.
Hope this helps, a bit.