The graphical interface seems to slow it down when it’s doing \n or \r or \r\n , etc.
Make the change from command prompt. I have a 7mb doc that is just numeric CSV data – like this 234, 345, 111, etc. From the command prompt the change to the file is practically instant.
Here I am replacing comma space with new line.
c:\emeditor /fi “, ” /x “c:\output2.txt” /rw “\r\n”
It is the same speed to go in the other direction.