There are some ideas to implement negative interest rates on bank accounts only but keeping cash by introducing a second cash currency that explicitly does not follow a stable peg. I.e. inflation targeting only has to be done on cash not bank accounts. Bank accounts will get price level targeting which means no inflation.
I guess what I don't understand by this proposal is how the exchange rate is actually maintained. Will they print a lot more cash to keep the exchange rate depreciating as thus? The devil will be in the detail of this.
https://blogs.imf.org/2019/02/05/cashing-in-how-to-make-nega...