XD currently doesn't have layers, but that is one of the features we will be working on. Please refer to to our roadmap document:
It mentions "Support for working with layers".
Sorry David what I meant to say was objects not layers
I've set up my artboards with a grid - when showing work I'd like to simple hide that object temporarily - currently i've been using opacity which is not ideal
For now, you could turn off the visibility of the objects (click off the eye icons in the Appearance section of the Property Inspector), and then lock the objects so you don't accidentally select them. To find them again later, just Cmd+A to Select All.