Go to preferences > Keys. Select Pattern Editor in the combo box (the list next to the load, save, reset buttons).
Clear the Move to Previous Row and Move to Next Row keybindings. Click on the “Move to Previous Row” and “Move to Next Row” keybindings, click in the box with the current keybinding, push the up and down key respectively and push the “assign” button. Then you can set the Move to Previous/Next row to whatever keys you want (perhaps Shift-Command-arrow key).