You can restore any preference to its original factory default.
In the left pane of the Preferences window, right-click on the Preferences folder and choose Restore Default from the context menu.
To restore a category of preferences
In the left pane of the Preferences window, expand a folder if necessary and then right-click on a category such as Animation Editor and choose Restore Default from the context menu.
To restore an individual preference
In the left pane of the Preferences window, select a folder.
The preferences are summarized in a grid in the right pane. Preferences that have been changed from their default values have a check mark in the Modified column (you may need to widen the Preferences window to see this column).
Click in the corresponding row of the Modified column to remove the check mark.
The preference reverts to its default value.
