en masse

[afaf]

ajouter une session en masse

context : enseignement

can we say in mass/ in volum

 

[Broff]

Do you have more context afaf?

 

[dalawat]

Je pense que In mass est acceptable comme traduction.

 

[ascoltate]

"session in mass" doesn't make sense in my variety of English.

If you mean a "group session", I would say that. But more context would be very useful...