You may be confusing a lack of braking when the accelerator pedal is released with a lack of regenerative braking. An EV can be set up so that no braking happens until the driver actually pushes the brake pedal, but that braking can be all by regeneration, to the limit of the abilities of the motor, controller, and battery. The Taycan does most of its braking by regeneration, but it generally doesn't brake until the driver asks it to.I recently managed to talk the local Porsche dealership into letting me test drive a Taycan. I was amazed - like zero regenerative braking - even with the braking turned on. I could not feel it at all. Dealer said it was to make it more like a normal Porsche. Never driven a normal Porsche - so I guess they don't have much decel. In comparison, my 2017 Smart Fortwo EV does a good job of slowing the car - though it could do more. Is it possible to increase the level of regenerative braking in a Smart Fortwo?
here's an article about Porsche's approach to regenerative braking control in the Taycan, and their reasons for it:
Why 2020 Porsche Taycan electric car won't have one-pedal driving
Notice that is says no "one-pedal driving", not no regeneration.
While my opinion doesn't matter, I like Porsche's approach much better than the one-pedal approach.
So, my guess is that you are looking for a more "one-pedal" approach for the Smart ForTwo, triggering more regenerative braking when the accelerator pedal is lifted. That's all controller programming, and I have no idea how you would change that.