How to make invisible plate hangers
Try command hook hanging strips , they are Velcro strips .
Over the years i have used Command hook strips for wall plate hangers with mixed results. Have had about 50% luck. If you go this route, be sure you have adequate support for you plates, over estimate the weight of the display for better results.
You can buy them easily at craft stores and online!
Instead of individual plate hangers, I would instead mount a floating shelf with an edge. These are often referred to as picture frame shelves . The lip, or edge will prevent the plates from sliding, and, as the hardware on a floating shelf is hidden, the eye will be drawn to your plates instead of to the hangers. You will be able to switch out the individual plates in your collection at any time with ever having to make any new holes in the wall.