Wow, I would find that sort of debugging, with listboxs cluttering my app's gui, very, very tedious.
In linux, all I need do is put a line like "writeln(SL.text)" in there when I need to see what really is in there. I usually put a line above it indicating which method generated that particular dump, helps in tracking how the content changes and helps in finding it to remove when no longer needed. And have a console window there in the background.
A little harder in Windows of course, debugln() and directing to a file ...
One day, we may be able to see a stringlist's content in the watches window, now, that might be cool but could also be messy ;-)
Davo