Yes, based on the Nano dimmer engineering sheet, S1 can be used to toggle the local load, while S2 can control a separate individual or other switch/dimmer devices directly ON/OFF.
Although I am unsure how to set Group Associations via SmartThings hub, perhaps someone else in the forum would be able to answer this one.
Parameter setting explaination and setting based on wanted application
I can advise the changes that you’ll need to make in order for this to work:
Parameter 123 [1 byte] will deal with how S1 controls in your network (Association Group 3)
Parameter 124 [1 byte] will deal with how S2 controls in your network. (Association Group 4)
The range of values are: 1 - 3
1: control the output load of itself
2: control other nodes only
3. control the output load of itself and other nodes.
To be very specific about what you are looking for:
S1 - control load only
S2 - control Group 4 associated devices only.
For this case you would set these parameter settings:
Parameter 123 [1 byte] = 1 //set only to control the local load
Parameter 124 [1 byte] = 2 //set to control Group Association 4 (maximum 5 devices per Z-Wave specifications over group associations)
By default, these settings are set to 3 for both load and association group control.
Most likely a new device handler would need to be developed to bring this application to life.