You can use this dialog to search for the occurrence of a text string within your project. The dialog looks like this:
You can choose to search the whole project or just the current page. The "Search range" widget allows you to specify where to search for the string. You can search in page names, page UIDs, object names, object UIDs, text objects, filenames, and in user code. Additionally, you can specify whether or not the search should be performed in a case-sensitive manner.