Find multiple lines in Notepad++
I wrote a multiline search and replace add on for Notepad++, check it out here: http://www.phdesign.com.au/programming/toolbucket-multi-line-search-plugin-for-notepad/
(source: phdesign.com.au)
As Xenovoyance suggests, it is possible with CTRL+R (also found in menu option TextFX > TextFX Quick > Find/Replace):
Just select your text to find, then invoke that option...
UPDATE: User Żabojad made me realise that in the latest releases of Notepad++, the "TextFX" plugin is not installed by default, so first you'll have to do one of two things:
The easiest one: Go to menu option Plugins > Plugin Manager > Show Plugin Manager, scroll the available plugin list to "TextFX Characters" and install it.
The above way should work, but otherwise you'll have go to this page : http://sourceforge.net/projects/npp-plugins/files/TextFX/TextFX%20v0.26/ and download file
TextFX.v0.26.unicode.bin.zip
then extract its contents (don't just copy zip file) to the \pluginssubfolder of the Notepad++ Install Folder
After restarting Notepad++ you'll see the menu entry TextFX.