How can I get Xcode to support tabs over the jump bar? I selected View -> Tab Bar to enable tabs in Xcode.

However, when I open a new file, it appears in the jump bar below the single existing tab and not as a new tab.

How do I get new files to appear as new tabs in Xcode? I've been spending some time trying different things out.
Double clicking your source files in the Navigator pane should make them appear in new tabs.