By default, the search is by prefix, e.g., above, "D" is typed and immediately "Dick" is selected, since that string starts with "D". However, you can use this statement:
...and then the entered text is used as a substring in the search:
Above, the "r" wouldn't have matched anything by default, since there's no string that starts with that letter. However, in the substring search, it matches "Harry", since there's an "r" in that string.
After the first matching node has been found, press F3 to jump to the next matching node and Shift-F3 to jump to the previous matching node.
Finally, you can also disable the quick search popup completely, which means that the JPanel will not appear at all when you type in the tree view: