Hi All, I am selling my house and was requested by the buyers to not have exposed romex under the sink for the garbage disposal. What options do I have to make the wire not exposed? Any ideas would be appreciated!

I currently have an outlet wired in my shop with 10/3 for my generator that goes to a double pole 30 amp breaker in my sub-panel (red and black goes to breaker, white to neutral bar, green to ground bar). I only use this to plug my generator into for back-powering the house (not used other than that). I am getting ready to purchase a welder and want to put the NEMA 6-50 welder outlet and the 4-prong generator outlet on the same circuit and use a 40 amp breaker and #8 wire. If I were to just have the welder on the circuit by itself, I would use 8/2, versus 8/3 for the generator outlet. If I put them on the same circuit, would I just run 8/3 to the 4 terminals of the generator outlet, then tie into the ground red and black and run 8/2 from there to the 3 terminals on the welder outlet?