All Super Neighbors will have a red dot in the neighbor bar.      
When you click on a neighbor in the main neighbor panel, you now have 'Set as Super-Neighbor' option. This will allow you to select one (or a few) neighbor(s) who  will be permanently hired to work your farms.  This will be especially nice  when you go on vacation or have to be absent from the game for a while.
You can also use the Order by Super-Neighbor option if you want to see all your Super Neighbors grouped together.
'Allow Planting' in the Edit Super-Neighbour window, allows them to plant crops in your farm. They will have the option of what to plant, the coins will be deducted from the farm owner's account, and the farm owner and the Super-Neighbour will EACH earn 2 XPs for each field planted.  When working as a Super Neighbor, as each job is finished on the farm, the next tool will be selected automatically until all jobs on that farm are finished.  The Super Neighbor is able to use the Manure Spreader and the Mobile Sprinkler, as long as the farm owner owns it.  When selecting a seed to plant, the Tool tip with the amount stored will reflect the amounts for the farm owner...same for the belts.

By checking the Design box, your Super Neighbours will be able to design at your farms. They will be able to go anytime to the farm you selected and start designing, you don't have to be online for this to work.  The SuperNeighbour will be able to use any Free Style tools that you own or that she/he owns. The Super Neighbor will see a red dot in the Farm Map showing which farm they can design on.

By ticking the "Allow Selling & Buying items,"  you allow your SN to use your/his  Dozer, MultiPlanter, Plower or Transplanter on your farm. They will be able to buy coin items using your coins, including plowing new fields; they will not be able to purchase or delete FarmCash items.