Rather than editing an onboarding process, we recommend Cloning an existing onboarding process and editing the Cloned version. This allows you to retain your original onboarding process in case you want to revert back.
Clone your existing onboarding process
First, go to onboarding processes. Press the v on the specific onboarding process to open the menu and select Clone.
The onboarding process will immediately be Cloned and you will see a new process with the same name but with (Cloned) appended to the name.