11 files declare their use of ShortcutSet in Drupal 9

ConfigTranslationListUiTest.php in core/modules/config_translation/tests/src/Functional/ConfigTranslationListUiTest.php

MigrateShortcutSetTest.php in core/modules/shortcut/tests/src/Kernel/Migrate/d7/MigrateShortcutSetTest.php

shortcut.module in core/modules/shortcut/shortcut.module

Allows users to manage customizable lists of shortcut links.

ShortcutLinksTest.php in core/modules/shortcut/tests/src/Functional/ShortcutLinksTest.php

ShortcutResourceTestBase.php in core/modules/shortcut/tests/src/Functional/Rest/ShortcutResourceTestBase.php

ShortcutSetResourceTestBase.php in core/modules/shortcut/tests/src/Functional/Rest/ShortcutSetResourceTestBase.php

ShortcutSetsTest.php in core/modules/shortcut/tests/src/Functional/ShortcutSetsTest.php

ShortcutSetTest.php in core/modules/jsonapi/tests/src/Functional/ShortcutSetTest.php

ShortcutTest.php in core/modules/jsonapi/tests/src/Functional/ShortcutTest.php

ShortcutTestBase.php in core/modules/shortcut/tests/src/Functional/ShortcutTestBase.php

SwitchShortcutSet.php in core/modules/shortcut/src/Form/SwitchShortcutSet.php