Strumming is possible with all modern Tone2 synths. From the technical side it is created by a quickly playing arpeggiator which stops after some notes.
Here is a guide how the arpeggiator in Icarus is setup for strumming:
1) Reset the arp with Tool->Reset
2) Set 'Arp loop point' to 'Stop 8'
3) Set 'Arp key mode' to 'Chord 6'
4) Set 'Arp speed' to '4/1 CLK'
