MusicXML export doesn't capture underscore in lyrics

In MuseScore an underscore ("_") placed at the end of a text syllable produces an extended underscore that extends to the lyrics of the next note (very useful feature for indicating elisions). But nothing about the underscore gets written to an exported MusicXML file. So if I create a MusicXML file and re-import that into MuseScore, the underscore is missing.

See Measure 2 in the attached example: The MuseScore file has an underscore in measure 2; the xml file it produces does not. And re-importing that xml file into MuseScore not surprisingly has the underscore missing. (Additionally the dynamic marking "pp" is not positioned properly, but that is a minor point).