What you need to do is shift from a single string, to an array. Then manually count the number of characters within that string and divide it by the maximum number of characters, use the mid() command to isolate the characters you want and place them inside each cell of the array. I do this all the time in my text adventure program for DarkBASIC Professional, the same logic applies to AGK.
You will either need to use print statments to display this, or you will need to dynamically generate text objects for each array entry.
Check out the UCF project there's several string processing functions there that can help speed this up for you.
http://forum.thegamecreators.com/?m=forum_view&t=193433&b=41
In regards to input, you can't access a multi-line text box, but you can keep adding lines to the master string. It won't be as pretty but it will work.
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Having said that, another way you could do this, is to create your own keyboard in the game. You could setup a sprite based keyboard yourself, and manually generate string characters from each input which get added into a string. This would avoid the input text box all together and you can simply type all this out directly into the game.
