No apparent "Generate Secret Token" button in GitLab Server setup

If I understand the docs correctly,

> The secret token is required to authenticate the webhook payloads received from GitLab Server. Use generate secret token from Advanced options or use your own. If you are a old plugin user and did not set a secret token previously and want secret token to applied to the hooks of your existing jobs, you can add the secret token and rescan your jobs. Existing hooks with new secret token will be applied.

there should be some "Advanced" button which exposes a "Generate Secret Token" button, which should call [`generateSecretToken`](https://github.com/jenkinsci/gitlab-branch-source-plugin/blob/8eb7bb2eee959956a5545b5fecfbe0add6b293dd/src/main/java/io/jenkins/plugins/gitlabserverconfig/servers/GitLabServer.java#L261-L267).

However, I can't see anywhere in this codebase that calls that function, or hooks up [the help text](https://github.com/jenkinsci/gitlab-branch-source-plugin/blob/8eb7bb2eee959956a5545b5fecfbe0add6b293dd/src/main/resources/io/jenkins/plugins/gitlabserverconfig/servers/GitLabServer/help-genButton.html).

Was this feature simply not implemented?

Based on that function, I'm using
```
dd if=/dev/random bs=16 count=1 2>/dev/null | md5sum -
```
to generate the secret token in the meantime.