I’m not sure how to accurately describe this… but as a newbie writer (and still not great at it), my mental grab bag of descriptive words and colorful phrases is rather limited. I see how successful authors paint such wonderful visual images and would like to do that also. (I know that’s mostly talent, but…) It would be great to have an add-on or tool that is more than a thesaurus… more like a writer’s word and phrase word bank, whose entries are linked together with tag words. I can also see this as being useful for authors that aren’t new, but have writer’s block. It could maybe come packed with a nice selection of words, synonyms, examples in sentences, colorful phrases, etc… but also have the ability for users to enter in their own entries and tags. Maybe I’m writing a story in which I need to describe a cold and windy night. I’ve tried being fresh with my description, but it just comes out very dull. However, if I would have had such a tool, I could have been making entries of descriptive words and phrases as I stumbled across them in novels, stories, magazines, etc. Then I could simply fire up Scrivener’s “writer’s word bank” and search for key words to see if I had recorded anything more colorful to help my own pitiful attempt at being descriptive. Thanks for your time and consideration, and I hope I’m explaining this in an understandable way. 
This might be close to what you’re looking for.