It is possible to redefine all keyboard menu shortcuts used by TeXShop. To do so, open the file ~/Library/TeXShop/Menus/KeyEquivalents.plist with TeXShop, read the comments at the top of the file, and edit the file to redefine selected menu shortcuts. Be sure to edit and save in UTF-8 format if you use Unicode characters.

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Redefining Keyboard Menu Shortcuts