My net worth tracker is my investment diary, but I keep things pretty simple so I tend to remember why I bought/sold something. I've never owned a lot of individual stocks and I've been indexing for 15 years.
For example, on my net worth statement I used to have a line (with a significant amount) for a money market fund with Vanguard. Well, that disappeared after the Great Recession when the funds were in danger of "breaking the buck" and the rate went below a savings account. I do remember back before 08/09 they paid better than a savings account.
Also my very first investment account at 16 was in a Janus 20 fund. That was invested heavily in tech stocks, and rose hugely through the late 90's. I remember at one time my father telling me he wished he had bought it! Then it crashed in 2001 during the tech crash and never recovered. After a year or so I just put it in an S&P 500 fund, and it's still there today.
For individual stocks, I've only every owned less than 10 total. I tend to dabble with a few hundred dollars of fun money, and then be reminded after a year or so why I don't own individual stocks. Then I sell them all.
If your investments are more complex or they change, it would be fun to write down some notes whenever you calculate your net worth. I do mine in Excel so I would just add a row and put some notes. It would be fun to look back on over time.