Sadly, addAction for some reason has the ancient and silly functionality of always referring to a script. That is to say, a typical addaction can look like this:
Player addaction ["Save game", "savegame.sqs"]
Using this action would then activate the script "savegame.sqs" which would be placed in your main mission directory. To make this script, simply create a new empty notepad .txt file, rename it 'savegame.sqs' (without the quotes), and then put this in it:
saveGame
hint "Game saved!"
exit
That's all you need to do to have endless savegames via addactions.
Wolfrug out.