While projects can be multi-Lingual, when in the editor view you do work on a language pair. So not at the same time.

You can have many language pairs open in in the editor view at the same time, in different tabs but I suspect this wont help you much.
While I dont fully understand your need and requirements, I am aware that users enjoy/need access to a reference language.
This at times is supported through the use of AnyTM - for the purpose of concordance searching and so on.

While projects can be multi-Lingual, when in the editor view you do work on a language pair. So not at the same time.

You can have many language pairs open in in the editor view at the same time, in different tabs but I suspect this wont help you much.
While I dont fully understand your need and requirements, I am aware that users enjoy/need access to a reference language.
This at times is supported through the use of AnyTM - for the purpose of concordance searching and so on.