A line style defines the pattern, color and thickness of a line. Line styles are used by electrical wiring and dimension styles. They are also used by elements, but you cannot change an element’s line style definition.
When you add or edit a line style through the Catalog Manager, the custom line style is saved with the catalog, and is only available when editing line styles in the catalog. If you add or edit a line style when editing your drawing, however, the customized line style is only available in the current project when editing elements in the drawing. The line styles library in the catalog remains unchanged. This is because the line styles library in the catalog is separate from the line styles library in the current project.
The reason that there is a project-specific line styles library is so that any line styles used in your project are always saved with the project, making it possible to share your project with others and always maintain your customized line styles.
If you want line styles that you have customized in your catalog to be available in your project-specific line styles library, or vice versa, you can use the Transfer tool to save the custom line styles to the external line styles library file (linestyles.klb), then import the custom line styles from the library file into the other line styles library.