This is a slightly odd suggestion, but I’m adding it only because I think it would be non-intuitively useful and actually fairly simple to add.

Would it be possible to add, as a piece of analytical data the halfway point between going to sleep and waking up.

You already track bedtime and time asleep so all the data is there. I’ve found it’s a really helpful metric to synchronise working times between groups in a way that bedtime or waketime isn’t, because it neatly includes larkness / owlness and amount of sleep into one more or less comparable figure.

I think it could produce some interesting correlations also.