From "template" and "description" I understand that you like to create an epub with description.
When selection "description" in the epub settings, you will see a dropdown at the bottom. All customized fields are available to add as an addition content to the catalog. You need first to create a customized field with the languages field and maybe more details
e.g. {tags} in {languages}
I have no clue why the content of the languages field is shorten.
If you like to rearrange the fields please have a look here:
https://manual.calibre-ebook.com/catalogs.html
In short: copy the template to a specific folder and update the xhtml.
You can remove fields but not add more than that one from the dialog mentioned above.