Search patterns may contain private data, and other people using your computer can see them in the search history. So you may wish to remove some history items.
Press the button with downward arrow (near Search for and Replace with fields) and right-click the item you want to remove. Another menu will appear:
Select Delete from this menu. If you select Clear history, all items will be removed.
You may also want to remove the trace of your replacements. Switch to the Undo tab, right-click the item you want to remove and select Delete. Note that if you removed the undo item, you will not be able to undo the replacement.