How to bulk change RD Gateway credentials?

I have many RDP connections in one folder and all of them use the same RD Gateway with separate credentials. Once in a while we have all passwords changed, including the password for RD Gateway. I figured I can use "Batch Edit" -> "Change saved credentials" to update all RD connections with the new credentials, but I cannot find how to do the same for RD Gateway. Is there a way?

Now when I understand different credentials storing options better, I realized that I should have used Credentials repository and when password changes only edit accounts in repository. But for now I have many connections with credentials for RD Gateway set individually. Is there a way to bulk update those?

Thank you!
Konstantin