I kinda don’t get what exactly you’re trying to do either. Are there MIDI notes on this track? Or just automation? If so, what automation? If it’s just say, controller 7 (volume) then I would not know where your note on or off commands are coming from, unless there is another Cubase track playing notes on the same synth using the same MIDI channel.
Just FYI, there are two ways that the MIDI spec handles note off: One is to send a note on command with its other values (note #, velocity, etc.) and then send a note off command with it’s other values (note #, velocity, etc) which changes the MIDI note status from note on status to note off status. The other way is to send a note on with its other values (note #, velocity, etc) and then to simply send a velocity of 0 for that note. This keeps the status as note on, which is known as running status, and overall uses less data for the same result. (nativley MIDI speed is very slow (3125 bytes per second) and before you could use USB to transmit MIDI from your synths to your computer, saving any data in the MIDI stream was very helpful) As far as I know, any recent synth will use a running status for note on/off data. (I give you this information so that you may be able to figure out a unique solution to your problem)
I don’t know if there’s a way to just send partial command from within Cubase, like note on with no note off information. The only way of doing what I think you want to do, would be to record a note from your MIDI keyboard and just leave the key depressed so it sends no note off information. Maybe tape it in a depressed position. Or if you want to be like Keith Emerson (who doesn’t?) use a dagger to keep the key depressed.
Let me know if this helps,