If you open the Navigation Pane in MS Word, e.g. with Ctrl+F in order to search for something in your document, sometimes you cannot close it using the Esc key, and you need to grab the mouse in order to aim this little x at the right top corner.

You can avoid this trouble by pressing (one after another, not all together) alt, then w, then k. This sequence is a toggle key, it lets you close the Navigation Pane, but if it is closed, it will open it.

Other useful Navigation Pane shortcuts include:

F6 / Shift+F6 — When the Navigation Pane is open, to switch forward / backwards between (1) Navigation Pane, (2) Bottom Taskbar, (3) Ribbon, and (4) Document

Tab / Shift+Tab — In the Navigation Pane, to move through the pane’s options