I’ve used Notepad++ extensively of late. One feature of this (free) editor is that when you select a word, it highlights all other occurrences of the same word in the document.
As I’m one of those writers who suffer from “repeatitis”, i.e. I tend to repeat words and expressions a lot, without being aware of it, a similar feature would be helpful in Scrivener.
Sure, ProWritingAid will catch these, but noticing the issue while I’m writing would be a boon.
The Search command will highlight all instances of the searched-for word.
Katherine
Ahh, yes, but that is a far cry from what I’m suggesting.
With Notepad++ functionality, duplication is immediately visible.
Using the search method, you’d have to know about recurring use and search word by word. Impractical for what I’m thinking about.
Notepad++ has its roots in being a programmer’s editor (I love it, and use it on every Windows system I am permitted to put it on, and even use it as my default text editor.) As such, as has functionality that is relevant for that setting.
Knowing that you’ve just typed your variable name correctly (and didn’t inadvertently make up a new and exciting one on the spot) is a huge boost for productivity for programming.
I think such a feature would be very useful: If there is a cursor on a word, then the same words would be highlighted in red in the visible text, and, for example, other forms of these words would be yellow. I would like this feature to be very simple, and the backlight is always performed when the cursor is in the word, without having to press any buttons. This is done in MS Visual Studio and it is very convenient for programmers. I think this will help writers a lot too.
You might try dragging a chunk of ordinary text into Visual Studio and experimenting there. I’m not sure you would enjoy this feature as much as you think. For me, at least, having highlighting like this jump around while I was typing would cause me to smash my computer into shiny bits.
I probably didn’t fully explain the details of my idea. Yes, of course, if you start searching for words to highlight among the entire project, no computer can stand it. I suggest that we limit ourselves exclusively to the current field of view. In my case, it’s about 3,000 characters on a fairly large screen. Moreover, there is a slight delay in starting the search after changing the cursor position. And of course, make this feature disabled, in case the user has weak computing power on his PC. And of course, the backlight should be as gentle as possible, looking literally half a tone different (as it happens in MSVisualStudio. I tried to work with the text there, but unfortunately VS highlights only c# language constructs in this way, and not just any text, which would be strange for programming tools). For me, the introduction of such an opportunity would allow us to immediately produce cleaner texts, and would reduce the time for the mechanical search for synonyms during proofreading.
(\b\w{n,}\b)\W+(?:\w+\W+){1,m}?\1
find the same words of n characters or more within m characters using Regular Expressions.
Exactly. As a professional developer, I don’t see any particular problem in implementing such a feature. If I had the source code and was immersed in this project, I think that implementing this behavior would take a maximum of a working day, including coffee breaks.
The idea was to show that using RegEx, this is already possible with the current build of Scrivener. 
I’m mean, the OP says they’ve tried this in another app and liked it so I guess they must have tested it and seen it works for them, but for my money I think this would be both annoying and useless.
Annoying, because (as @kewms suggests, above) having highlighting pop all over the screen just because I selected a word would be distracting.
Useless because, well we’re not coders checking to make sure we’ve got our functions and strings correctly typed to match perfectly. Repeated words often don’t have identical spelling…
I’ve given this a lot of thought. At least I think I have. Thinking is not my speciality. My girlfriend thinks. She’s the thinker. So I changed. I want to change. My girlfriend says I’m changing. But sometimes there are too many changes.
(The good news, though, is that people sometimes find that me not liking something is a good enough reason to do it! 
)
But you do understand the difference between: “write a word, press a keyboard shortcut, see if I used it a paragraph above; write the next word, press a keyboard shortcut…” and “write a word, immediately see that I have already used it two sentences earlier; write the next word, see that I haven’t used it in the foreseeable future;… etc.”
On the one hand you talk about doing this during proofreading, now you want it as a standard function while you write. I question if you have any sense of the disaster you’re suggesting. Get a third-party app to do it. Being a speedy developer, you should be able to resolve all 75 suggestions it pops up within a few seconds between sips of coffee.
I’m sorry, but do you understand the difference between text highlighting and popups? I’m saying that such a feature would probably drastically reduce the amount of proofreading, because it would help you immediately see repetitions on the go and use synonyms while writing.
I agree, if you implement this feature in the form of bright, flashy colors, then few people will like it. Unfortunately, I can’t insert a screenshot here of how it looks in MS Visual Studio, but it’s implemented quite unobtrusively there, and the highlighting of single expressions differs from the rest of the text by literally a quarter of a tone.
And, if you noticed, in my sentence I also talked about “different forms of the word”.:
I’ve given this a lot of thought. At least I think I have. Thinking is not my speciality. My girlfriend thinks. She’s the thinker.
I do, but it should either be a non-modal highlight while typing, just as a subtle warning, or a report like something ProWritingAid might do when checking a manuscript in Editing.
I kind of like the first use, it’s like checking and warning for spelling errors, but for Writing Style errors…
I think Scrivener do as much as it can to help Writers write professionaly.
I repeat, my idea is that it should be highlighting words with color. And in any case, not tooltips or popups. I’m sorry if my English is bad and I couldn’t explain my idea correctly.
Ah, well. You have found a break in my example. You broke it. How easily it breaks. Is it broken beyond repair, though? Maybe I should just go have breakfast.
Good luck coding for the English language!
Perhaps it’s because I’m not Shakespeare, but for my taste, using “think,Thinking,thinks” is not pretty, but “break,broken”, although it doesn’t match, is quite acceptable. I don’t write in English, but in my language it’s a good idea to use a single root word within adjacent paragraphs. But if the conjugation or declension of a word greatly changes its root, then this is quite acceptable.
And, by the way, “breaks,breakfast” - I wouldn’t use it twice side by side either, and would choose a synonym. So the backlight would help me in this case.
Which language would like it coded for?