Layer 1: hold any letter
Hold A → à á â ä æ ã å ā. Hold $ → ¢ £ ¥ €. Press the number under your pick, or click it. If holding repeats instead, restore it: defaults write -g ApplePressAndHoldEnabled -bool true.
Layer 2: Option shortcuts + dead keys
Direct: Option + G →, Option + R → ®, Option + C → ç, Option + S → ß, Option + O → ø, Option + ' → æ. Dead keys (press, release, then the letter): Option + E acute, Option + ` grave, Option + U umlaut, Option + N tilde, Option + I circumflex.
Layer 3: Character Viewer
Control + Command + Space anywhere. Search “arrow”, “check”, “fraction” — double-click inserts. Click the expand icon for the full browser with Unicode blocks, code points and font variants. Add it permanently to the menu bar under System Settings → Keyboard → Text Input → “Show Input menu in menu bar”.
Layer 4: ABC Extended
System Settings → Keyboard → Text Input → Edit → + → “ABC – Extended”. New dead keys appear: Option + A then a vowel → macron (ā), Option + B → breve, Option + V → caron (š). Essential for Māori, Pinyin and Eastern European names. Switch back to U.S. for coding — Extended remaps several programmer keys.