I didn’t test this from within the node-red add-on as I don’t have a test-version up and running but does work with node. Use at your own risk.
node reencrypt <old key> <flows_cred.js> <new key> <flow_cred_new.js>
example usage:
node reencrypt oldCredentialsSecret ./flows_cred.js newCredentialsSecret ./flows_cred_new.js
https://gist.github.com/zachowj/193c1d7ee53833a1e18358597e589106