@Bader-Alharbi said in I want to compare two files and bookmark the lines containing similar words:
is there a regex to add the line number in multiple places in the line?
Regular expressions cannot count (they have no concept of “increment a number”). Your two options inside Notepad++ are using the Column Editor like you’ve already discovered, or using a scripting plugin like PythonScript and using the full power of a programming language to influence the text in the open file. (I actually just answered a question earlier today on that same concept.)
apply it to different files with a different number of lines.
as linked in that other topic (and the links refenced there), you can make a macro that will do the begin/end-select for column mode… and if you combined that with other controls, like the Ctrl+Home to go to the start of the file, and Ctrl+End to go to the end, you could have a macro that does the zeroeth-column select in the macro, then manually type Alt+C to bring up the column editor and insert the numbers, then you could use another regex (using multiple capture groups) to distribute the number from the beginning of the line to the various locations throughout the line that you need