How multiple inputs monitors are managed by OSX ?

Hi.

I have a 2013 Mac Pro (D300) and a 6MP Eizo RX650 monitor. The monitor has to be connected with 2 DP inputs in order to address its native resolution.

With this setup, I am not able to display a full extended desktop. What I have is two desktops side-by-side, with two menu bars and one Dock on the main desktop. Like when two separated monitors are connected to the computer, but here on the same only screen.

This creates a very confusing and unsatisfying user experience, especially in the field this monitor is dedicated to. I was wondering if there is a way (system or third-party) to extend the desktop on the whole surface of the screen ?

Best regards,

RW