History entries scroll off the top of the list as new entries are added at the bottom. But it is possible to retain an entry permanently. Enter History, put the highlight bar on the entry to be retained and hit Insert. Retention can be toggled off by hitting Insert again.
I use History with many commands, particularly \, F, X and C. To make sure that your responses are recorded in XTree's History file, always exit Xtree properly by Q or Alt-Q.
Tom Ruben