Cannot find "New" option in FileItem dialog (macOS)

On macOS, the FileItem dialog does not have a field for entering a filename, as though the "ShouldExist" flag is always set. To reproduce in modelbuilder:

• Load the attached filetest.sbt
• For the "Output File" item, click the "Browse" button
• The navigation widget doesn't have anywhere to enter/create a new file (as best I can tell). Screenshot attached.

Also:

• You can select a folder in the dialog and add the file to the QLineEdit, so there is a workaround.
• The screenshot was taken from a modelbuilder built with Qt 5.12.6 (binary install). Bane S originally reported the problem using a recent download of our nightly builds.
• Don't think this is relevant, but the resource browser shows TWO "export" items for the one/instanced attribute.