I use my MacBook Pro (Retina w/ MagSafe) a lot in the kitchen, but the easiest place to put the power adapter (right behind the faucet) means it's near water and often falls off when I move the laptop.

This adapter bracket mounts on the underneath lip of our sink, getting the power adapter out of the way and securely holds it. The bracket could mount under any desk or shelf to keep your adapter close by but held securely. Two holes allow for mounting with screws but I used 3M VHB tape to secure my bracket.

The bracket also has "ears" to let you wind up the MacBook.

Both the STL and Fusion 360 files are included.

Once the bracket is mounted, slide in the power adapter and you're done.