Fibaro Dimmer 2 (FGD-212)

[Eibersite]

Domoticz 2020.2
I'm using a Fibaro Dimmer 2 (FGD-212) with a Mono-stable input (button)/Momentary Switch and so far I am very satisfied with the dimmer.

In Domoticz there is a Instance 2.
Can someone explain to me what is for, switching it gives no result?

Instance 2.JPG (21.34 KiB) Viewed 569 times

And can someone explain to me how to use S2.
Switching S2 with a Mono-stable input (button)/Momentary Switch doesn't seem to do anything at all.

S2.JPG (15.76 KiB) Viewed 569 times

[cos4x4]

this is what i found in the manual.

The Dimmer 2 provides the association of five groups:
1st Association Group „Lifeline” reports state of the device. Main
Z-Wave+ network controller should be added to this group. The „Lifeline”
group can handle only one device. It is not recommended to
modify this group.
2nd Association Group „On/Off (S1)” is assigned to switch no. 1.
Sends BASIC command class frame according to the state of the device.
3rd Association Group „Dimmer (S1)” is assigned to switch no. 1.
Sends MULTILEVEL SWITCH command class frame. Allows sending
dim/brighten command to associated devices.
4th Association Group „On/Off (S2)” is assigned to switch no. 2.
Sends BASIC command class frame according to the state of the device.
5th Association Group „Dimmer (S2)” is assigned to switch no. 2.
Sends MULTILEVEL SWITCH command class frame. Allows sending
dim/brighten command to associated devices.