Not by adding a custom button. In my scenario, when my program runs, it does some fast operations that take only one or two seconds and then goes into deep sleep. While developing, it was difficult for me to reset the board manually to flash it again. So I just delayed the deep sleep by 60 seconds when it first booted up. It helped for my scenario of “edit the code-reflash” loop, but it is not a generic solution.
I needed the reset button because of the fast deep sleep. So my solution to the problem of needing the reset button due to going into deep sleep, was just not to go into deep sleep immediately.