Hello, @blake-g.-barrington, @peterjones, @coises and All, Here is my version to get duplicate lines, separated by any number of lines ( whatever they are : true empty lines, blank lines or lines with text ), even zero line : MARK (?-si)^(.+)(?=(.*\R)+\1$) As said by @Peterjones, and after some tests, this kind of regex get into trouble when the bunch of lines, between two duplicate lines, exceeds 15,000 empty lines about ! Now, Let’s suppose you create this text file : first 0002 0003 0004 0005 .... .... .... 9997 9998 9999 10000 first Then the (?-si)^(.+)(?=(.*\R)+\1$) regex returns : Correct result until the number of the in-between lines does not exceed 1,600, with the message 1 match in entire file Correct result until the number of the in-between lines does not exceed 12,000, although the error message Find Invalid Regular Expression ( So F.I.R.E. !! ) occurs ! NO result at all if the number of lines is over 12,000 lines, with, of course, the error message Find Invalid Regular Expression Best Regards, guy038 P.S. : I should add that my Windows11 laptop has 32 Gb of memory !

The syntax file can be created by means of user-defined language. But how to apply this user-defined language automatically when Smart Math is enabled for the current file/document? OK, sorted it out: call NPPM_GETNBUSERLANG first to get the number of UDLs; then iterate through all the UDLs and call GetMenuStringW; once the menu item string matches my UDL name, I’ve identified my UDL menu id; after that, call NPPM_MENUCOMMAND with the obtained UDL menu id. Here is an example withUDL applied: [image: 1788696158249-d17e9134-3e1a-4b20-b7e9-62b16dbc4eff-image.jpeg] It’s a pity that I can’t make the keyword colors (such as function colors) to be dependent on the active color theme/style. I mean, for dark color themes these keywords in blue look too dark, so the color must be changed for dark themes.