The editor needs to be able to, directly in the site-access (English for example), translate content into another language existing into the site (French for example).

With this particular configuration there is no option to translate from eZ Webin into one of the secondary languages. There is a translate from English dropdown menu, but you are not able to translate into any other language.

Steps to reproduce

1. Setup a multi-lingual site with one locale per siteaccess and language fallback switched off.

For example english is the main language in the eng siteaccess. It has the following configuration:

[RegionalSettings]
Locale=eng-GB
ContentObjectLocale=eng-GB
ShowUntranslatedObjects=disabled
SiteLanguageList[]=eng-GB
TextTranslation=disabled

The french siteaccess has the following configuration:

[RegionalSettings]
Locale=fre-FR
ContentObjectLocale=fre-FR
ShowUntranslatedObjects=disabled
SiteLanguageList[]=fre-FR
TextTranslation=enabled

2. Try to edit a content object within the eZ Webin front-end editor.

RESULT: There is no option to translate into any of the other languages available within the site.