And I agree that you can work to find the sweet spot to allow the car to coast, but it's harder than it needs to be.
This is a subtle question and it might not make sense at first, but here goes...
Why do you want to "coast"? I think that is the issue right there.
"Coasting" is simply one point on an infinitely variable scale of forward force that starts with "holy crap my eyeballs are crushing my brain" and ends with "I'm being held back by my seat belt" and the fact that one point in that spectrum happens to map to "no power is flowing from the batteries to the motors" is irrelevant.
When you think about "the sweet spot" on the pedal and "coasting" vs "regen braking" vs "accelerating", then your brain is actively focused on the wrong thing - the mechanism itself and the state of the system rather than where it should be focused - which is the driving environment.
Instead you should be considering closing speeds and how quickly you will arrive at a point where you might need to stop, or not want to stop, or where you may want to still be retaining some of your speed. Think of where you want to go and how fast. Think "closing too fast" or "no longer closing fast enough" and your foot will do the right thing without having to worry about where the "coasting sweep spot" is. You should never be thinking about coasting or regen, you should be thinking about lane position and following distance and thinking ahead to how the next 10-20 seconds of forward progress will work out compared to the traffic conditions.
This is a little easier to get the hang of if you have a long hill with a stop sign at the top (there is a great one here in SF on 17th headed up towards Twin Peaks with a fair bit of cross traffic at times). Don't think of where you want to switch between regen/coast/acceleration modes, think of how the cars are progressing through the intersection and how you are tracking them. In this case you will be varying the amount of motive force up the hill constantly, but it will always be an application of power - this example will never end up in the "coasting" state.
But the thing is, your brain doesn't need to conceive of "coasting state" or the uphill equivalent thereof - your brain only has to worry about how quickly you are pushing the car up the hill. Eventually you should get good enough to progress smoothly up the hill with little variation in speed and, if necessary, be able to hold it in a stationary position easily with your foot on the accelerator. In this experiment your brain isn't calculating "what is the appropriate amount of power to hold the car still on this hill and where is that position for the accelerator and when is my foot exactly in that spot", rather your brain is thinking "am I moving forward or not and am I getting closer to the car in front or not" and your foot will magically do the right thing. That is the only thought you should be having and your brain is actually well designed by evolution to do just that.
After getting used to that, the level road equivalent is pretty much exactly the same thing, it just so happens that the range of pedal positions your internal feedback loop will use to control forward progress and traffic positioning will happen to include a spot that is characterized as "coasting" if you analyze the power flow in the system - but you don't need to be thinking about what is going on in the system, or even aware of it - just think of how close that car is getting to you and whether you are happy with that...
