I think it would be useful for a couple of reasons to have a column in the time chart next to pitstops saying which lap a driver's last stop was on?
Especially in a long race with many drivers, when you pit and come out, chances are you'll be amongst drivers you haven't been keeping a close eye on so it would be handy to know if the drivers above and below had stopped recently or are more likely to be stopping soon.
If you log in mid way through a race it would give a far better idea of what is happening. Not just with other drivers but also whether you pitted on the planned lap or have fuel calc issues.