"Can an outlet be behind the dishwasher?"

No. "The installation cabinet must be clean and free of any obstructions" and see Figure 2 of the installation instructions.

"Any idea how much space there is behind the dishwasher after it is installed?"

Assuming cabinet is 24" deep, none.

Samsung dishwashers aren't known for their reliability per CR subscriber surveys. You might want to consider the Bosch SHEM3AY55N if it's available in your area.

Adding to what wdccruise said, electrical codes forbid putting a DW's electrical outlet in the space behind a built-in dishwasher. Code requires putting the outlet where it will be readily accessible for quickly disconnecting the power to the dishwasher when needed. That's why you frequently find their outlets in adjoining sink cabinets.

Put the outlet under the sink next to the dishwasher. you'll run your dishwasher appliance cord through an opening between the two cabinets that you drill.

You also cannot use a gfi outlet. It must be on a gfi breaker as its not easily accessible per code.

Understood. Now another question is can I run romex behind the dishwasher? I'll need to move the outlet and only way to do this is if I run romex to an outlet on the other side of the dishwasher behind it. The outlet I have circled I would cancel out and run the wire lower behind the wall and to the left inside the cabinet under the sink along the outside of the wall. I would go in the wall but there is a 4x4 to the left of the existing outlet.

1. Is there an outlet for a garbage disposal inside the sink cabinet?
2. The electrical box for the existing outlet is attached to a stud on its left-hand side, right? Where do the wires entering the electrical box originate?
3. A stud can be drilled or notched.

1. No, which is my predicament. I have an outlet on the right behind the microwave that I will be using for the dishwasher.

2. You are correct but it is not just 1 stud. It is a 4x4 sandwiched with 2x4s.

3. I would think it is going to be too hard to drill through about 8" of wood.

You try planning all this out but unfortunately layouts change after drywall is in. My idea is to run a romex down the inside of the wall then pop it out through the drywall to the cabinet next to it and put an outlet in there. Not sure if that is to code, though.

"I have an outlet on the right behind the microwave that I will be using for the dishwasher."

I don't see an outlet behind the microwave in the photo. But as the Romex cable comes in from the right, I don't see why you couldn't disconnect the Romex from the old outlet and pull it out of its electrical box; cut a hole in the drywall below the microwave; install a new electrical box and outlet there; fish out the Romex from inside the wall and attach it to the new outlet.

The microwave would have no power but it doesn't have any now.

There actually is an outlet behind the microwave as noted in this pic that was added before the cabinets were installed. I'll cancel the existing one but need to add another one next to the pipes. But I want to make sure I can drop a wire from the existing box inside the drywall, punch the Romex through the drywall then run a connection for an outlet inside the sink cabinet.

edit:

Got confirmation from an electrician that says it's not a good idea. Something about moisture and exposed wiring. lol. I have a circuit under the house so I'm just gonna come up from underneath and install an outlet. Thanks all for the advise and recommendations.