An error occurred while saving the commentS Renalds commented
I believe a workaround might be to change your task bar settings to not span both displays, then move your task bar to the secondary monitor. It's not ideal, but should make for a less cluttered presentation space. Edit: Actually, this doesn't work as expected... The notification center moves to the secondary monitor, but I believe notifications still pop up on the primary. Still, your presentation space would be less cluttered.