March 2026, by the fact there is still no smart highlighting over lines, would fully indicate there is no intention to add such a feature.

… or, at the least, that nobody asked for it. I pointed out how to make an official feature request 6 years ago, but if nobody followed those instructions and actually made an official feature request, then the developer never saw that anyone wanted that feature. Making the request doesn’t guarantee that it will be implemented; but if no one makes a request, that effectively guarantees that it won’t be implemented.

I tried the Mark All method, worked nicely. However, one important note, one needs to make sure exact words in the find box is turned off, any non-alphanumericals, including space, and definitely EOL chars, will cause a non-match.

I do not want to permanently highlight them

I think @Ekopalypse 's suggested method is actually better than Smart Highlighting for this purpose. And…it isn’t really permanent, you can clear it later.

Plus you can make it really fast to implement and clear by using keyboard combinations rather than mousing through the menus.

And the killer feature part: Even if Smart Highlighting did what you wanted, you couldn’t quickly navigate to far apart versions of the duplicate text sections, you’d have to visually look for them. With Eko’s method, and he pointed this out, you can quickly jump to the next occurrence, even if very far away from the original.

I’m not a developer on Notepad++, but I really don’t see Smart Highlighting being changed to cross line-boundaries.

If this is a missing feature or defect, should I post this somewhere else so it gets implemented or fixed? Where should I port it?

My guess is that Smart Highlighting was intentionally designed to not do multi-line (probably easier to implement that way); but that’s just a guess.

If you would like to request a feature, see our FAQ about feature requests, and please understand that just requesting a feature, even in the official location, is not a guarantee that it will be implemented.

The thing is that I do not want to permanently highlight them. I just want to go through and quickly find the occurrences as I go through the logs. I just want to use the Smart Highlighting feature.

Testing
1 … 2 … 3
Testing
1 … 2 … 3
4 … 5 … 6
Testing
1 … 2 … 3
4 … 5 … 6
7 … 8 … 9

Currently you can mark those lines (e.g. Search->MarkAll->using 1st style)
and jump through the matches with Search->Jump down->1st style