Redmine issue statuses name the stages an issue can move through, such as New, In Progress, Closed, or a team-specific waiting state. Creating a status is needed when a project lifecycle has a state that should appear in issue lists, filters, and history instead of being written only as a note.
Issue statuses are site-level administration values. A new status is not automatically available to every tracker and role; Redmine uses the workflow matrix to decide which users can move an issue from one status to another.
Use a short status name, add a plain description, and decide whether the status should close issues before saving. After the status exists, add at least one workflow transition for the target tracker and role, then test the change with a project member account.
Related: How to create a Redmine tracker
Related: How to create a Redmine issue
https://redmine.example.net/issue_statuses
Replace the hostname with the URL for your Redmine site.
Enable Issue closed only for terminal states that should count as closed issues.
Redmine can warn that no tracker uses the status until a workflow transition points to it.
https://redmine.example.net/workflows/edit
Clear Only display statuses that are used by this tracker when the new status is hidden from the matrix.
The selected matrix should allow Support Lead users to move Maintenance issues from New to Waiting for Vendor.
Related: How to configure a Redmine workflow
The issue must be in a current status that the workflow allows to move into the new status.

The issue history should record the status change from New to Waiting for Vendor.