What does simmer slowly mean with white soybeans?
I explain what the technical definition between a simmer, boil and roiling boil is here.  A slow simmer would be a very thin but continuous stream of bubbles rising from the bottom of the pot. 

Parboiling does not mean maximum heat. Parboiling means that you're only boiling until it's part of the way cooked, not completely cooked; so, you're cooking mostly at a full boil, then reducing heat to a simmer to finish them.  This ensures they don't overcook.

You'll have to figure what setting a boil and a simmer are on your plate, as it depends on the power and size of your pot.   On a stove, I'd expect 2 to be a simmer, and about 3 as a full boil, but it varies from one model to another.