I’ve had trouble to do that but it’s finally not that hard.
In a theme component, modify your handlebar component to have this code:
{{#each categories as |c|}}
...some stuff before the bell...
{{category-notifications-button
value=c.notification_level
onChange=(action "changeCategoryNotificationLevel" c)
}}
...some stuff after the bell...
{{/each}}
If you don’t know how to do it, Johani’s tutorial is a perfect “first place to look”.
And if you find how to do the same with tags, please tell me ! I can’t find a way to do it.