Please share with Pamela that it is possible today. If you're viewing the Outlne, select the File menu and then Print. In the Print dialog, there is a section called Format. In the pull down list, select one of the Indented options (e.g. Indented Large Font, Indented Small Font).
I'm slightly confused by this suggestion - when I print in Outline view, the subtopics are indented. If you want to have more control over the process and the appearance of the outcome, you can export to Word or Excel.
If you are talking about exporting an outline in OPML format, there is an issue as MM2012 for Windows can't do this, while I understand that MM for the Mac can. However the Map2Excel add-in has an option to export a text file outline. This produces an indented list in HTML format which should be able to be converted to OPML.