I know I've seen it before, but not sure where.

You mean the actual times? In Scheduler Tab, Job Constraints: Twilight.

Not sure if there is/was a way to change the default sun dip (18⁰) somewhere, if that is what you looked for.

There is an option in the configuration of Ekos -> Scheduler for offseting dusk and dawn, but I'm not sure it works or where it is documented what are the units of the values you need to enter. Yesterday my scheduler stopped at 6 AM and there was still another 20-30 minutes of darkness I could have been used ... and I just didn't manage to get the scheduler to continue running for them.

The Dusk/Dawn offsets (Configure KStars/Ekos/Scheduler) work, though I can never remember which way is + vs - for each setting. Check in the scheduler to see what it is currently using at the Twilight checkbox.

Mireia - there is an interacting setting you might have missed. Also in the Ekos/Scheduler settings tab: The 2nd line in Offsets is "Pre-dawn". I do not understand what is the intended purpose, or why the default value is 30minutes. But if you change it to 0 then the times shown for Twilight in the Scheduler itself accurately reflect when a job will start and when it will be stopped for dawn.

Ok, that makes lots of sense and matches what I showed the other day that it stopped 30 minutes before twlight. Will remove those 30 minutes ! Thanks