Importing both jpg and nef files to LR

You can-

1) Open the Metadata panel for the Filename.

2) On the Filmstrip Filter bar you will see the Filename of the selected image.

3) If you Press KB [i]  in Loupe or Develop views you can toggle Information through 3-states {on1/on2/off}

Change Develop View options with [CMD/CTRL+J]

Show Expanded Cells in Library View can show filename on the Thumbnail border- [CMD/CTRL+J}

Sort the Library Grid view by File Type-

Run a Custom Metadata Filter to show (and select) one FileType. (eg. click on JPEG)

You can also uncheck the option in Preferences>General to NOT import the JPGs into the Library. (They are then considered a JPG 'Sidecar' file, not visible in the Library at all.)

If you want both the RAW and JPG Previews in the catalog, and be able to edit either, then you must check this option that will treat JPEG files as separate photos when you Import, an then use one of the options above to note the file-type.

Any more suggestions? Sure to be!