Smaller Power Brick

In most applications, there will be a separate power plug just for the sprinkler controller, but sometimes you have to share the plug with other devices, but Rachio makes it difficult with the huge power brick. My suggestion, make a smaller power brick or have the transformer further down the wire, like PC charging cables, but have it wall mountable.

Smaller would be difficult, as Racho uses AC voltage and transformers can’t easily be made smaller without loosing power rating.
Are you using your controller outdoors? If so Rachio sells an outdoor enclosure specifically designed to house the power supply within the enclosure itself. Otherwise a cheap extension cord would allow you to move the supply away from the socket and perhaps tape it to the wall with a doublesided tape.