many editors will do it... or you could just get a txt file from same place you get the m3u file... Just scroll the same list that you got the m3u list from and you will see the txt version
You could just change the file extension to .txt and then use an editor like notepad++ to keep the basic format inside and make whatever changes, etc. I edited my m3u in notepad++ and kept a text copy along with the m3u.