How do I join lines in Notepad++?
Menu "Search" > "Replace" (or Ctrl + H)
Set "Find what" to
\r\n
Set "Replace with" to (empty string)
Enable "Regular expression"
Click "Find next"
Click "Replace" to change the matching EOL or click "Find next" to skip to the next match.
Repeat as necessary.
Before:
1st line 2nd line 3rd line
After:
1st line 2nd line 3rd line