I do something very similar with my connected dishwasher and Home Assistant. It's way over-engineered due various limitations/odd design choices with the API and the machine itself), but I've got it setup to store the selected program when I press a button on a Hue Tap switch, and then it turns on and runs that program when our off-peak energy rate kicks in - which is better than working out how much to set on the delay timer each evening to start it in the right ballpark.

Of course I've also got it setup to announce the selected program, and that the machine is "armed" via Google Home when the button is pressed, and again each time the door is opened/closed to add new dishes. And it sends notifications to my phone when the program starts (mostly for debugging purposes) and ends.

Like I said, massively over-engineered but it was a fun little project.

I don't have a smart washing machine (yet) but I do have it plugged into a smart plug with an energy monitor. When the power usage drops to near zero for more than 2 minutes it sends a notification to tell me that the cycle is done.