Yes. It's super easy provided your MIDI controller is recognized by Studio One. For instance, I have an Emu Xboard MIDI controller connected to Studio One. If I turn a knob on my MIDI controller, Studio One immediately notices it here:

You can see in the pic above that Studio One recognized knob 1 on my Xboard MIDI controller. I can then right-click on a send level in a track and assign it to that knob. Here you can see that I right-clicked on the send level to Bus 1 and can assign it to knob 1 on my MIDI controller.

After the send level is assigned to the knob on my MIDI controller I can control the send level in real-time with the knob. I can also record the knob movement to create an automation envelope.