I'm creating this issue, because already two key customers have requested this option.
By design, TMGMT supports ONE source and ONE target language per job.
However, (original) design doesn't matter too much, in case users define their real requirements different.
In order to support multiple target languages at the same time in UI, we either need to
- Change the design of a job
- Create multiple jobs through the UI
The cart might manage a real job (then it won't help), or it is an extra layer on top of the system without the per-job conditions/limitation.
#1416504: Add Cart system →
One of the early ideas was to collect stuff in a/multiple named carts (different source languages allowed, no target language yet to be selected) and then create jobs out of it. The system would then help to do so.
Note that currently already we have a multiple-job creation wizard if you select multiple target languages in the translate tab. However, this does not apply for the job level.
Also, with the job creation UI, one design direction was to allow setting the target language even earlier to limit the perspective to that target language only. Then, the N target language columns in the overview would be reduced to one. D8 went that direction for the locale UI (to do translation). This will also bring us away from multi target languages.
Similar is the design direction to allow setting a source language: Usually, all source objects are added in their source language. Setting the job source language would list only content that allows to be used as source in a certain language - which might already be a translation. This chaining sometimes is required.
Tweaking this all is not that easy :-)