That's normal.
If you want to access all the lines in the editbox, you can use $did(dname,id,N) to access the Nth line (you could make a loop to get them all), you can also use $didtok to get all the lines separated by a given character.
However, it seems like your typical usage is to open your dialog and paste the content of your clipboard into the editbox.
First, you could handle the clipboard when you open your dialog with the 'init' event and with $cb: https://en.wikichip.org/wiki/mirc/identifiers/$cb
That way you wouldn't even have to paste.
But I suggest you look at pre-made dialog that are available with $input and the like, for example you can use something as simple as //echo $count($?,$chr(44)) and paste the clipboard there, no need for a custom dialog really.
