Not a bug, depends on your Jenkins version. You need to go to admin configurations and press save once. Then the textboxes should be populated in the job's configuration. The value is still required in the actual textbox, whether it's an override or not.

Changed from Major Bug to Minor Improvement since it is functioning currently as intended. May change in future to use a checkbox to signify if an override should be applied or not. Currently tho

Override Host: <some value>
Override Port: <some value>

The value has to be provided, regardless if it's overridden or not. The purpose of the admin config is to pre-populate those text boxes but that requires one save action of the admin config page. If you have any questions please feel free to ask and i will try to clarify.

Ok I get it and indeed after saving once the admin page, the fields got filled.
Maybe adding a line in the wiki will avoid confusions when the has just been installed

Let's leave the ticket open, i may consider changing how the functionality works in the future but for now, you can see wiki changes here.

Thanks for the wiki modification, it will be clearer to follow.