Tip: show this menu with the Alt+N, U keyboard shortcut (type an extra "M" to show them all).

Tips:
• The quickest way to go? Double-click to insert any letter and hit Esc to return to Word.
• Notice that Microsoft keeps track of your "Recently used symbols" on a separate row.
• When a symbol is selected, its keyboard shortcut (if any) is shown at the bottom (like hitting the Ctrl+Alt+E hotkey to insert the Euro currency symbol - see screenshot above).
(The AutoCorrect button lets you create instead a text sequence that will be auto-replaced with the symbol when you type it - like the built-in "->" that becomes an arrow once you press Space.)