I would also like this system to be introduced, tried the comma thing but that didn't work.
I would like to add all .pdf, .docs, .ppts etc to open in a new window/tab, but I can only add a single specification.
Temporary solution was to specify all links containing '/wp-content/uploads/' to open a blank target, but that would also include every file in that directory, I've excluded jpgs, but then I'm also missing out on excluding audio, video, jpegs, gifs, png etc.
So a way you can enter multiple Includes and Excludes would be a great enhancement, otherwise this is on the right track and very useful plugin to avoid having to trawl through 100+ page WP and add _blank manually to the links. Thanks!