Integrations Hub for Jira

Read or Update Protected fields via Integrations Hub for Jira

Create an Integration flow
Add trigger when the integration shall happen (Event or Webhook)
Add a Web Action
In the Method set POST
In the URL set the URL copied from the Protected Fields api admin page
Generate a token in Protected Fields api admin page and add that to the URL like this
url?token=your_token
Add the issueKey in the URL &issueKey={{issueKey}}
In the body section add

{
  "fieldId":"customfield_21345",
  "value":"30000"
}