Remove All Lines except lines with a Specific Word - Notepad++

Very Simple way

1. Press CTRL+F and Type the word or pattern.
2. Click on "Find all in Current Document"

4) You get the filtered lines. Copy them to a new file.

1- Assume this is your file and you want to delete all lines which doesn't have "WScript" in it.

2- Do a regex find as shown below. BookMark all the required lines.

3- Then remove the unmarked lines