Notepad++ ignoring search results on same line

To answer the question there is not that functionality, but it would be a good idea. Feature requests for Notepad++ can be submitted through IdeaTorrent.

A work around is to use a regular expression that swallows the rest of the line. For example is you want to find lines containing abc you can search for '.*abc.*' under regular expressions and that will find every line with abc but will only list it once.

As Andrew mentioned, the best workaround I could find was RegEx.
I wanted the specific text to still be highlighted in the search results, and Notepad++ RegEx doesn't support variable length lookbehind, so I ended up using a negative lookahead like this

ABC(?!.*ABC)

That way it only finds that last instance of ABC on any given line, but it still highlights ABC.