When I ingest files shot with a Nikon D200 set to nef plus jpg only the jpg thumbnails show up in PM4.2. How do I view the nef images?
You can temporarily split them by toggling the "Combined RAW+JPEG" command on View menu (Command-J on Mac, Ctrl-J on Windows). If you don't ever want them joined together, then go into Photo Mechanic's Preferences and click on the Contact Sheet tab. Uncheck the "Combine RAW+JPEG into single thumbnail" checkbox.
Keeping them joined has many benefits because while joined, the following things happen to both files synchronously: tagging, color classification, renaming, and IPTC captioning. You can choose whether the RAW or the JPEG are used when editing (Launching tab in Preferences: "When in RAW+JPEG mode, editing a photo will:") and you can choose a specific editor for each file type (Launching tab in Preferences: "Assign specific editing applications for each file type:"). They are also grouped together when you drag and drop the JPEG into another folder, the RAW file goes with it.
HTH,
-Kirk