When performing a search or replace with the Find and Replace tool window, SlickEdit can use text that is selected in the editor as the initial search/replace string. For example, if you make a selection and press Ctrl+F, the selected text is displayed in the Search for field of the tool window. To enable this option, from the main menu, click Tools > Options > General, then select the Search tab and check the option Selected text (if exists).
Note that if there is no selection, SlickEdit uses either history retrieval or the word at the cursor to initialize the search/replace string (depending on the option you have specified on the Search tab).