@Clydie – yes, you can change modes while driving (moving to EV might not work due the the described limitations).

I also switch from D to B and back as I drive the local hills. B increases the “no gas/no brake” electric regeneration – there’s more drag on the car as it regenerates more power. (According to the display a lesser degree of this happens even in D). In hybrid terms, it’s sort of like very slightly but continually pressing the brake whenever not using the accellerator in order to slow by regenerating, but not enough to activate the brake pads. In conventional terms it’s like using engine braking, except you get some of the energy back.