Just above the XML Code textbox are two buttons. The left button applies the contents of the XML Code textbox to the Sample Display. The next button saves the changes as a language definition file, using the same naming approach as a normal export - xxx.lng, where xxx is the name of the language as seen in the Language Frame language listbox.

Caution: gbXML recreates the content of the XML Code textbox every time an attribute is changed. So if you make manual changes, then change an attribute, your manual changes will be lost! Save your manual changes before making any further edits with gbXML!