Dorico currently prevents the computer from going to sleep automatically. This is a side-effect of the fact that it has Cubase’s audio engine. In a pro audio application you don’t want the machine going to sleep because it has to be ready to play or record at any time. However, we know that Dorico’s user base has different requirements, and we do intend to add the ability for it to allow the machine to sleep after an interval.
In my experience I haven’t had problems with it preventing sleep when closing the lid or explicitly asking the machine to sleep, so maybe that depends on your soundcard drivers?
I find it generally very reliable to put my PC to sleep every night, ever since Vista. Most of the problems that users experience are down to poor soundcard drivers.