Hi.
In TextEdit, once you have opened the "Find" window, try typing option-tab or option-return as the search "character". This might work. I remember that this trick used to work in older versions of Microsoft Word when trying to insert a tab in tables - because the tab key was actually used to move between table cells, option-tab was programmed to insert a tab character instead of moving into the next cell. Similarly, when using dialogs such as "Find" in most applications, tab is used to move between one text entry area and the next in a dialog, the same way that tab is used on web pages to move between certain selectable items on the page. Also, as return is usually used to substitute for clicking on the OK button, option-return might be the way to insert the return character. Good luck.