When the Use in-place completion option (see Selecting the completed input) is off, all keyboard completion gestures raise a modal dialog presenting a choice of completion options.
Also, clicking the 
button to the right of a text input pane raises a modal completion dialog.
You can navigate the choice with
Up
and
Down
and you can select the desired completion at any time with the
Return
key, double-click, or click the
OK
button. To cancel the attempt to complete, press
Escape
.
LispWorks IDE User Guide (Unix version) - 25 Nov 2011