How to display categories by alphabet on sidebar and how to display tags on sidebar?

[Lilly]

Do you have this setting enabled?

Admin guide to tags in Discourse

If you haven’t read it already, It’s Time We Talked About Tags provides an overview of how tags can be used as an organizational tool. Configuring Tags Tag settings can be found in your admin panel under the “Tags” section of your site settings. [tag-site-settings] Tagging is enabled by default. To disable tags, ensure that the tagging_enabled setting is unchecked. Creating and applying tags Tags are created upon first usage. When composing or editing a topic, a us…

Creating and applying tags

Tags are created upon first usage.