If someone - like me - comes here to find an answer. Meanwhile there is a channel called notification_send1 on my FGD212 Dimmer 2 and probably most other devices with notification capabilities (also those RGB Fibaro Outlet Switches).
I set the duration and effect of the alarm using HABmin:
Items:
Number work_lights_alarm "Arbeitszimmer Licht Alarm" {channel="zwave:device:bridge:node18:notification_send1"}
Sending the number 1 to the item will start the effect (1). After the timeout (2) the blinking stops and the dimmer returns to its previous state. The Fibaro Dimmer blinks at 0,5 Hz (1 second on, 1 second off). I could have easily done this in a rule but I am grateful for Fibaro and Chris and all contributers to have this feature readily available.