I already have an invite flow that users will arrive at and go through when signing up, now I want to let users create invites for other users. That page does not mention anything about that. It seems to be about adding a flow that asks user for details such as an email address and then they get their account.

In my case users have already gone through that and want to invite someone else.

With invitations, you can either email an enrollment invitation URL to one or more specific recipients with pre-defined credentials, or you can email a URL to users, who can then log in and define their own credentials.

I already have enrollment invitation URLs. Just not automatically. I wrote a script that uses the API for that purpose.

The docs even mention this about the flow:

Enrollment (2 Stage)

Flow: right-click here and save the file.

Sign-up flow for new users, which prompts them for their username, email, password and name. No verification is done. Users are also immediately logged on after this flow.

Nope. Not what the question is about. This requires an admin user to create an invitation in the admin backend. I want a way to let users do that.