Can't move Camera Limit widget

Hi there,

I'm following this tutorial youtube.com/watch

At some point, he grabs the cross widget to change the camera limit. From my understanding, he is simply clicking on the widget and then he moves it but it doesn't work here (I'm using 2.8). Is there a particular shortcut I'm supposed to use? By the way, in his case, I can see there's an overlayed cross appearing when he moves the mouse over the cross. In my case, the color of the cross doesn't change. Thanks