Got this reply today:
Hello there,
Transifex hosts a lot of PHP projects but, having first searched for similar requests, there is no demand for supporting multi-dimensional arrays. Our roadmap is a really loaded one and we occasionally override the next thing to do if and only if there is a massive request for a particular feature. That said, it's not something that will go live soon but it may be implemented in the future, if a critical mass of requests is reached.
Thank you for your understanding,
Themis
--
The Transifex Team
So we needa change our code and langfiles if we want to use Transifex.