The history list of a tool stores the most recent events which have been carried out in that tool, or the most recent objects which have been browsed in it.
The History > Items submenu provides a list of these events (or objects), allowing you to repeat any of them (or browse them again) by choosing them from the menu. This gives you an easy way of repeating forms in the Listener, inspecting objects or browsing classes again, revisiting searches, and so on.
The menu lists the last ten unique items to have entered the history list of the active window. Because each entry is unique, some items may have occurred more than ten events ago.
If the editor is the active window, the History > Items submenu lists the buffers currently open.
The easiest way of repeating an event from the history list is to choose it from the History > Items submenu. There may be times, though, when this is inconvenient (the items on the list may be too long to be able to distinguish between them easily, or you might want to repeat an item that occurred more than ten events ago). In such cases, there are three commands which offer an alternative way of choosing items.
Choose History > Previous to perform the previous item in the history list of the tool. This is usually the most recent event you have performed, but may not be (if, for instance, the last action was itself an event that was already on the history list).
Choose History > Modify to remove items from the History > Items menu. A dialog appears that contains all of the items in the current History menu. Select the items you wish to retain , and click OK . Any items which were not selected in the dialog are removed from the history list.
Note: another way to keep track of items that you're interested in (such as appear in the history lists of various tools) is to place them on the Object Clipboard. See The Object Clipboard for more details.
LispWorks IDE User Guide (Macintosh version) - 12 Feb 2015