Is there a way to reset the capital or equity to its initial value when the script is running halfway? I would like to reset it when it met a certain condition.

I tried searching the manual but it doesn't mention about this.

Sure, I have a method to force fees or credits to your balance, which you can use to reset your equity:
https://www.vitaltrades.com/2020/07/14/adding-exact-fee-and-credit-calculations-to-zorro/