If the tree has the focus (one of its nodes has the focus), pressing an alphanumeric key (not capitals) will move the selection to a node beginning with the typed character (if one exists) and open a search edit box with that character.
The screenshot above was taken after typing an <fl> when the root of the tree was selected. Continue typing to jump to the first node that matches the character set typed so far.
If no match is found then no node is selected.
The search facility is not case-sensitive:
To clear the search box, do either of the following: