I do not have any way of keeping track of my seedlings on the computer but I have garden maps and have them marked with signs. I do take a picture of each seedling, print it up and write down the stats on the back of the picture. I have done that for many years and it works for me.
I wanted to edit this and say I really do have a way to keep track of seedlings with the Plant Step program. I just have to utilize it, which I have not. Will have to further look into that.