NST Manager is utilizing almost every single Nest function/API that is available. Nest currently has not made any API available for:
- Nest Secure (nothing for the alarm system)
- Nest Hello (nothing for the doorbell functionality) - Treated as a camera only.
- Nothing available for reading Filter notifications/reminders from Nest.
- No way to detect power outage for a device direct from Nest
- The new Remote Sensors
- Nest x Yale Lock
If it’s not available from Nest, NST Manager cannot provide the functionality.
I have seen nothing posted in the Developer or Community section as to when/if any of the above will be made available. 
https://developers.nest.com/documentation/cloud/get-started?nav=true