12 files declare their use of CKEditor5PluginDefinition in Drupal 10

ckeditor5.api.php in core/modules/ckeditor5/ckeditor5.api.php

Documentation related to CKEditor 5.

CKEditor5.php in core/modules/ckeditor5/src/Plugin/Editor/CKEditor5.php

CKEditor5Plugin.php in core/modules/ckeditor5/src/Annotation/CKEditor5Plugin.php

ckeditor5_drupalelementstyle_test.module in core/modules/ckeditor5/tests/modules/ckeditor5_drupalelementstyle_test/ckeditor5_drupalelementstyle_test.module

ConfigurablePluginTest.php in core/modules/ckeditor5/tests/src/Kernel/ConfigurablePluginTest.php

EnabledConfigurablePluginsConstraintValidator.php in core/modules/ckeditor5/src/Plugin/Validation/Constraint/EnabledConfigurablePluginsConstraintValidator.php

FundamentalCompatibilityConstraintValidator.php in core/modules/ckeditor5/src/Plugin/Validation/Constraint/FundamentalCompatibilityConstraintValidator.php

Media.php in core/modules/ckeditor5/src/Plugin/CKEditor5Plugin/Media.php

PluginManagerDependentValidatorTrait.php in core/modules/ckeditor5/src/Plugin/Validation/Constraint/PluginManagerDependentValidatorTrait.php

SmartDefaultSettingsTest.php in core/modules/ckeditor5/tests/src/Unit/SmartDefaultSettingsTest.php

StyleSensibleElementConstraintValidator.php in core/modules/ckeditor5/src/Plugin/Validation/Constraint/StyleSensibleElementConstraintValidator.php

ToolbarItemConditionsMetConstraintValidator.php in core/modules/ckeditor5/src/Plugin/Validation/Constraint/ToolbarItemConditionsMetConstraintValidator.php