Seam Selection
This tool can be used in the standard viewports or in the UV Editor. It's only available in Edge mode and essentially functions like the familiar Edge Path Selection tools. The Attribute Manager provides various options and settings to control the selection of seam edges. Seams are evaluated by some of the UV tools to split or cut the UV unwrap along these edges. Seams are stored in a special Edge Selection Tag and can also be manipulated via its settings.
Selected edges can also be added to or removed from a Seam selection of a Seams Selection Tag at any time. To do this, use the Mark Seams and Unmark Seams commands, which are also available in the > menu or as buttons in the Seams Tag.