In current versions of MuseScore, the palette search box is at the top of the window instead of the bottom. Also, you no longer need to define your own shortcut for palette search - Ctrl+F9 to jump directly there (whereas F9 by itself opens and closes the palette window).

When using the mouse, remember, you no longer need - or want - to double-click palette elements in order to apply them. Single-click does the job. But when accessing the palette by keyboard, Enter applies the current element, just as shown in the video.