The documentation for this from GitLab is below.
(excerpt from this-- GitLab's documentation on Jira integration) .
The bold text is the point of my question as I do not understand where in Jira you would "mouse over the link for the transition." It does not do this in the Workflow view (diagram or text).
Obtaining a transition ID
In the most recent Jira user interface, you can no longer see transition IDs in the workflow administration UI. You can get the ID you need in either of the following ways:
- By using the API, with a request like
<a href="https://yourcompany.atlassian.net/rest/api/2/issue/ISSUE-123/transitions" target="_blank" rel="nofollow noopener noreferrer">https://yourcompany.atlassian.net/rest/api/2/issue/ISSUE-123/transitions</a> using an issue that is in the appropriate “open” state - By mousing over the link for the transition you want and looking for the “action” parameter in the URL