Over the years I have created a number of spreadsheets in which various life data points are recorded. The most obviously QS one being aggregation of exercise time and number of steps involved. The duration is taken from a GPS tracking app on my iPhone and the steps are from the iOS Health app. I could easily pullout distance covered too but to date have not because I would have to extract terrain data but I do not have that for early years. A second one is my daily blood pressure readings which I transcribe into Apple Notes before processing/visualising the fluctuations with Apple Numbers. Oh how I wish that Apple would implement its patent for taking blood pressure readings with an Apple Watch thereby removing a source of error with transcription from the analogue machine I am using. Every few months I produce a graph of my blood pressures to discuss with my GP. Also have one for sex which has to be updated manually.
Other spreadsheets are a little obscure. For example, the weekly shopping list with all the items purchased from the local supermarkets. There is a sheet for each of the main supermarket, a second one that has a butchery counter, and a third that has a good range of gluten-free products. (Includes sheets for food manufactuers who I will not buy from for ethical reasons.) Looking to enhance it with links to the supermarkets web sites and their home delivery service. This is perhaps not an identifiable quantified self usage but it does mean that I neither forget anything nor over buy things. I am the worst shopper for supermarkets for not being swayed by offers on things that I have little if any need for. Only respond to offers if I was going to buy an item anyway or know, because I marked the spreadsheet thus, that I will need to purchase the item soon.
When doing my recent degree course I kept a spreadsheet of books I read or was reading. Included course texts and other genres fiction, other subject domains, etc. Again probably not a QS record but I did note that some one else in these forums was looking into tracking their quantity and quality of reading.
One recent quasi-success has been tracking why my Italian coffee machine has not been producing crema! I already had a sheet to predict when the next descale was required and the likely date for the next full service. (The machine has had two since purchase eight years ago.) Recorded my process from which brand and roast of coffee used, through when I drew the water, how I filled the filter head — whether each refill tamped and how hard, whether I flushed the filterhead or not after use. The desired result (of a Guinness style head of crema) was random. But it seems focusing my attention on this spreadsheet altered me to the general issue as a recent news report suggested that not tamping the refils but using a very loose amount of ground coffee produced better results (and for coffee shop reduced costs). Since reading that piece there has been 100% success in crema, Every measure of coffee is now aerated before being scooped up; shaking the storage jar! And of course a consequent lowering of my frustration.
But this all raises the question of what other variables I could record.