In recent releases of QlikView there's a great feature called the Expression Overview. To see it, select Properties->Expression Overview (or, hold down the ctrl key, the alt key and the E key at the same time). This overview shows you where the expressions are in your document, it can show you the text of the expression, it will allow you make changes to the expression, you can search for specific text in the expressions like a field name or variable name, and you can do mass changes with the search and replace functionality.
There's no HELP button but you can make the Expression Overview Help screen appear if you press your F1 button. The Help screen will explain the available functions.
As always, if you are going to make serious changes to a document it's a good idea to make a backup copy of the document first, just in case you make a mistake and want to restore the document back the way it was.
My own preference, when I want to search for a particular kind of expression or if I just want to review all of the expressions in a report looking for problems and opportunities is to use the Export button to export all of the Expression Overview data. A box will appear asking for the pathname to use for the exported text file. The text file is a tab-delimited text file that can be reviewed with Notepad or Wordpad or a spreadsheet (or loaded into QlikView!).
The exported Expression Overview text file makes an excellent addition to documentation for a complex report for those of you who are required to produce documentation.