SQL statement history is designed to ease recalling and re-executing statements you have previously executed. Choose View SQL history from the SQL menu to bring up a dialog where you can choose which SQL statement must be inserted into the editor instead of current one. Point with the mouse on a statement in a history to view its full text in a hint.
For quick navigation through executed statements you may use Previous SQL and Next SQL buttons. Previous SQL goes down the stack and Next SQL goes up.
The history clears when application is closed or SQL document is saved or opened, so you have to save your queries for long-term use. SQL history is not available when working with an opened file.