Search history

Aba saves the last 20 search parameters, including a pattern, a replacement, and search modes. To repeat one of the previous searches, press the button with a downward arrow (near Search for and Replace with fields) and select an item from the left menu.

By default, Aba immediately starts searching as you are selecting items from the menu. If the preview is undesired, you can turn it off in the Options dialog.

You can clear the entire search history or remove individual items by right-clicking them and selecting Delete from the shortcut menu. Unfortunately, you cannot open this menu by pressing Shift+F10 or the shortcut menu key on your keyboard. It's a limitation of Microsoft Windows. You can press Backspace instead.

Hotkey Action
Alt+Down Open the search history menu (when you are in Search for or Replace with fields)
Backspace Open the shortcut menu for removing search history items
1..9, 0 Open the first, the second, etc. element in search history

This is a page from Aba Search and Replace help file.