De acordo com este link :
This feature is disabled by default, but a quick trip to the Preferences will get you using the new auto-complete feature in no time at all. Go to Settings -> Preferences, and switch to the Backup/Auto-competion tab. At the bottom of that screen you’ll see where you can enable auto-completion, and you can optionally turn on the “show function parameters” feature as well. What’s that do? Here’s an example of me using a PHP function, and you’ll notice that it gives me a friendly reminder of the parameters the function takes:
Tenha em mente que isso é suportado apenas no Notepad ++ 5.0 ou posterior ...