I really loved this add-on & it didn't seem have been updated, so I played with it a bit. I've changed the default memory to 1000 lines & the default lines shown to 20. It seems to work fine, but I let me know if there's any problems.

You can record chat from several different channels or just from one and you can change how many lines it will keep track of. Channels you can record from include say, yell, emotes, party, guild, raid & system.

Click on the little square at the bottom left of the chatbox to open the program. You'll have to copy (using ctrl-c) & paste the text to a file to save it. Use the boxes at the top to chose which channels you want to see. It will record all of them, though.