You’re quite right, above all it needs to be simple! The beauty of WW is that it’s largely automatic when set up, and the time-slot grid makes it very intuitive to manually add or remove slots on an ad-hoc basis.
I’m going to run for a few days with multiple Charge windows and see how I get on (23:00-06:00[hold charge] & 06:00-23:00[discharge]). Obviously I’ll lose out on the optimal selection of low-cost slots, but hopefully this won’t be significant.
I am concerned that this approach still doesn’t stop my house battery occasionally dumping into the car, in situations when the last automatic slot ends before the car is fully charged. The only real solution to this would be your suggested ‘exclusion hold-charge' window in the Advanced tab?