To be fair, that is not a common request, at least from what I have experienced here on the Community.
I'm not quite sure what you are looking for here.... But will make an attempt anyway...
You appear to have configured three time periods:
Mornings - Sunrise -15 minutes to Sunrise, essentially the 15 minutes leading up to Sunrise
Days / Evenings - 8 - 9am (I am thinking this should be 8am - 9pm)
Nights - 10-11pm
Before I try to cover your questions, a couple of questions would include:
What about Sunrise - 8am?
What about 9am/pm to 10pm?
I'm guessing 11pm to Sunrise -15 minutes is of great interest, but worth considering
So back to your original questions....
The time periods you have setup are meant to then allow you to configure different activation and off configurations in Room Lighting during these times. I personally drive my "time periods" using modes rather than fixed time periods, or even those derived using Sunrise like you have used. Each to their own, that is not the point here, it is more that this is the purpose of what have configured, you now have the option to define different behaviour during these times.
I would need to check the documentation to check how this may be articulated, but that is at least my take on this... others can dissect the official explanation.
I am probably not in best situation to answer your question, so hopefully others may chime in.
I would suggest working through your example and solution you need to implement before getting too deep into documentation changes, for now..... That said, I get the inclination to suggest a chance off the bat for new users, but just leave it for now and assess at the end of your situation.
If I understand what you want correctly, for your 'Night' time period that you dont want the lights to come on, just untick under the 'Act' column. That will stop the lights activating during that time period.
Maybe, maybe not, as we're missing the main Room Lights page, so not sure exactly how you are automating the lights (you mention motion in a later post). Mind sharing the main page setup ?
For example, "Vary lighting using time periods" could allow you to achieve what you want by splitting the day groups into week/weekend columns and then unchecking the "Act" (stands for activate) column for the weekday time period(s) you don't want Room Lights to control a particular device .
There are other ways to limit activation, but that is done in the activation options under "Means to activate lights" (from the main config page).
Each row defines the beginning of a period and the settings in that period remain valid until the start of the next period.
Day groups are read across (columns), time periods down (rows).
Maybe I'm also in for a doco change... But will hold-back for now and stick to my orignial call for seeing through the discussion and seeing what falls out of that before making any drastic changes....