Question about Garmin Vivoactive 4S

Ok too bad... but thanks for the answers :-)

Unfortunately no. I would also wish for that ;-)
As CarrieS already said: There is only an alarm function with vibration alarm, but this is not coordinated with the sleep phases.
(There is, however, a sleep phase profile - which you can then view in the app).

Alarm by vibration alarm yes, but no sleep phase alarm function, but via time setting.