What you can observe on your instance is correct behavior. To edit list of mixins from crx/de you have to use dedicated option from contextual menu, select Mixins... option
From code you can use addMixin and removeMixin methods from Node api:
What you can observe on your instance is correct behavior. To edit list of mixins from crx/de you have to use dedicated option from contextual menu, select Mixins... option
From code you can use addMixin and removeMixin methods from Node api: