Since I do lots of guitar takes and have both my hands full, it made sense for me to trigger Cubase with my feet. And since I didn't find any information about how to do this and had to figure it on my own, I thought that I'd share it here.
SS has a transport scene which can be used in Standalone mode. This scene uses MMC (Midi Machine Control) commands to communicate with most of the DAWs. So the only thing you have to do is to set Cubase to receive these commands.
If you look at the picture you will see two areas in green circles which are numbered 1 and 2:
Step 1: CTRL click on SYNC button on the Cubase Transport (Green Circle 1) to open the Project Sync Setup window.
Step 2: Tick the "MMC Slave Active" checkbox (Green Circle 2), select SSCOM in the "MMC Input" drop down menu and change the "MMC Device ID" to 1 since this is the Softstep's MMC ID. Leave the MMC Output alone.
And you're done