They actually go into the database. There's a custom attribute table that holds the definitions and values field to hold the individual saved values.
I'd probably just add a custom attribute to a reservation to capture this information
You want to add someone but you don't want them to know they've been added? Can you give me an example of how you'd use this?
Add participant or attendee without registration
This is already supported by enabling guest participation
There is a config option in the AD config called use.sso. Just set it to true.
I just tried that and it's working fine. If you want to take this offline you can contact me directly to help me reproduce it.
Is that directory writeable? I just tried this and it is working in my test environment.