I often run several queries in parallel. They usually last between 1 minute and 1 hour.

Thanks to Explain Plan I know more or less how much time they will last, but I nearly always forget when I started them.

So I would love to see a "running since" or a "chronometer" in the status bar of each test/sql window.

yeah, me too! Maybe 'started executing at hh:mm:ss'.

And, when the execution ends it should not only tell the total time, but the start/end times (I sometimes come back and wonder when a window was run).

This is on the list of enhancement requests.