I hit Scrivener's feature request forum and did a search on "adverbs." Who'd have guessed I wasn't the first person to have the idea. The request was denied, but one of the comments referenced The Hemingway Editor.
The Hemingway Editor is a web-based app, but there is a downloadable desktop app. I only used the web-based one. It allows you to paste text into the editor, or compose within it.
It grades your writing based on the number of sentences and words. The lower the grade, the better the writing. The grade may be commiserate with school grade levels - i.e., if it's rated a grade 4, a 4th grader could read it.
Pros:You can paste a surprising amount of text into that window and it doesn't crash. Like, more than 5,500 words.
The mechanism to find difficult-to-read sentences is nuanced enough that it has two levels of difficulty, "hard" and "very hard."
You can format the text in the editor. There are options to make lists, use bold and italics, and the normal rich-text options.
Cons:It doesn't find all the adverbs. It finds the ones with an "ly" ending, but misses "only," "even," "never," and some others.
If you paste a lot of words into the app, it can get confused. Switching the toggle from Edit to Write, pasting the text, and toggling back to Edit fixes this.
Pasting from Scrivener really confused Hemingway. The hard returns didn't transfer over, and this had an impact on the grading and on which sentences it thought were "very difficult." Often, adding a hard return where there should have been one downgraded the difficulty level and upped my grade.
It really wants you to write short sentences. Sentences without clauses. Simple sentences, with only one comma. That's great sometimes, but gets old after a while. I blame Hemingway himself for that one.