In the regular find window, there's that arrow button you can click
to get a multi line text field where to enter your search query,
but I don't see it when I do a search in whole project, which is
kind of a pain when looking for lengthy pieces of code...

Do you know command-E? It places the selection on the find clipboard.
99% of the time, I want to find something which is already in my
source, and never actually type it in the find dialog text fields

Thanks for the tip. But the situation I'm often confronted to in my job is editing whole sites coded by others that have the same exact HTML on millions of pages and I really need to use the project wide search and replace feature in order to be anywhere close to productive... If there's is any chance to implement the same collapse window thinggy from the regular search in the future, it would be great. Thanks again for your help.