A Preference Document
A document window will display a list of the keys/values in a preference file, with the key being the first column, the value being the last column, and in between it will display the class, or type, of the value. Note that these are the default column positions; you can reorder the columns if you wish.
Simple Editing
The values are what you primarily wish to edit if you are just making changes to an application’s preferences. When making such changes, you will not want to edit the key name, nor will you want to change the class of the value — changing the key’s name will make that an unknown key which the application will ignore, and changing the class of a value will very likely cause the application to crash when you next launch it.
Tips
In addition to double clicking on the field you wish to edit, you can also press Return ( ⏎ ) to begin editing the “Key” column, Space ( ␣ ) to pop up the Class menu, and Shift-Return ( ⇧⏎ ) to begin editing the “Value” column. Pressing Tab ( → ) in the “Key” column while editing the key will switch to editing the “Value” column, and pressing Shift-Tab ( ⇧→ ) in the “Value” column while editing the value will switch to editing the “Key” column.
(Note: the Tab key usage described above works with the columns in their default positions.)
All changes are undo-able, and can be undone past a save.
If you have edited a running application's preferences, you will need to relaunch the application for it to notice the changes you have made.