If not all then almost all pod specs are immutable, meaning that you can't change them without destroying the old pod and creating a new one with desired parameters. There is no way to edit pod volume list without recreating it.
The reason behind this is that pods aren't meant to be immortal. Pods meant to be temporary units that can be spawned/destroyed according to scheduler needs. In general, you need a workload object that does pod management for you (a Deployement, StatefulSet, Job, or DaemonSet, depenging on deployment strategy and application nature).
There are two ways to edit a file in an existing pod: either by using kubectl exec and console commands to edit the file in place, or kubectl cp to copy an already edited file into the pod. I advise you against both of these, because this is not permanent. Better backup the necessary data, switch deployment type to Deployment with one replica, then go with mounting a configMap as you read on the Internet.