@JCSullivan Just drag the txt files to main calibre window
The above will get you txt files to add empty book records, you can then get the metadata for them, automatically as normal
Then you create another entry, by making a m3u file of items you want in your VLC player or whatever you use.
Put the m3u playlist file on desktop and just drag it to calibre's main window, check it works, by clicking on the coverview image.
Now you just have to merge the two entries - ie keep the metadata from one and the shortcut from the other - simple
(click on the metadata rich entry then ctrclick on the on the m3u entry, press ALT+Shift+M)
For audiobooks, I just have a checkmark column instead - but I use this method for Video playback of series I have kept as it's really useful.
Just click on the image and the series opens up in the player. You can also use it for URL's, to open sites etc.
Probably not explained it very well.