As well as examining objects in the Inspector, you can destructively modify the contents of any composite object.
This sort of activity is particularly useful when debugging; you might inspect an object and see that it contains incorrect values. Using the options available you can modify the values in the slots, before continuing execution of a program.
Choose Slots > Set to change the value of any selected slots. A dialog appears into which you can type a new value for the items you have selected. Previously entered values are available via a dropdown in this dialog.
Choose Slots > Paste to paste the contents of the clipboard into the currently selected items.
LispWorks IDE User Guide (Macintosh version) - 25 Nov 2011