Add multi-word name or phrase to dictionary?

Unfortunately that isn't an option in InDesign, as you have discovered. You can create custom list of word in a .txt file and import that word list into your user dictionary, but InDesign recognizes the individual words because they are separated by a space, a tab, or a paragraph return. That's the dealbreaker.

The only "outside the box" solution I can think of is to add the words with an underline in place of a space, i.e., blu_karrot, and use a GREP style to make the underline transparent with a character style (and I reduced the typesize by half because it was too wide). 

~Barb