You can display the links on an object's Traceability Links tab as a single list or grouped by object type or link type by clicking the Types and Grouping tool and selecting the appropriate grouping command.
When you select Group by Object Type or Group by Link Type, the different types of objects or links are displayed on separate sub-tabs. To add a link to a new object type or with a new link type, click the plus sign on the leftmost sub-tab.