Mac OS X makes extensive use of xml files; xml is a structured language closely related to html.

TeXShop uses five xml files for configuration: completion.plist, autocompletion.plist, KeyEquivalents.plist, Macros_Latex.plist, and Macros_Context.plist. These files are used to configure the Latex Panel, Auto Completion, the Keyboard Menu Shortcuts, and the Macros menu. Details are given below. These files are automatically created in subfolders of ~/Library/TeXShop when TeXShop first runs.

Files of type plist are ordinary text files. They can be opened and edited with TeXShop, TextEdit, or other text editors. Each of the files except Macros.plist has a comment at the top explaining the file format. Editing is straightforward, but somewhat tedious. Macros_Latex.plist and Macros_Context.plist will never need to be edited because TeXShop has a Macro Editor built in.

If a plist file contains unicode characters, it needs to be edited and saved in UTF-8 format. Before opening such a file in TeXShop, change the TeXShop encoding preference to UTF-8. Then edit and save the file. Then change the encoding preference back to the original value. The default value is MacOSRoman if you did not reset it earlier.

Users with the Developer distribution installed will discover that double clicking a .plist file opens the file in a program named Property List Editor. Property List Editor is useful for editing plist files, but it is buggy and does not display the comments. So it is better to use TeXShop.

How do I configure TeXShop?
.plist Files