AEM: Tag Translation Language Dropdown - Adding more languages

In AEM, the language dropdown in the tag editor (Settings → Tags → Edit → Language) shows only a small subset of available languages, even when all language nodes are correctly defined under /apps/wcm/core/resources/languages.

Solution

There are three possible root causes:

1. Missing or incomplete languages[] property on /content/cq:tags — the tag UI reads this property directly to populate the dropdown. Add it to /content/_cq_tags/.content.xml in your ui.content module. Use mode="update" in your filter — not mode="merge", which silently skips property updates on already-existing nodes.
2. Language locale not defined in AEM — overlay the missing locale under /apps/wcm/core/resources/languages in your ui.apps module.
3. Permissions — add rep:readProperties allow ACE on /content/cq:tags for the relevant user group via Repo Init.

The most common culprit is #1, combined with the merge vs update filter mode confusion.

Full write-up with code snippets and filter mode comparison:

Why Your AEMaaCS Tag Translation Language Dropdown Is Missing Languages — And How to Fix It