I took a look at the databas of the SF, and figured out I could do this:
 

update tot_target

set tot_target.transl = tot_source.transl

from transl_object_transl tot_target

join transl_object_transl tot_source

    on tot_target.transl_object_id = tot_source.transl_object_id

where tot_source.model_id = 'GUI_TRANSL_ENG'

    and tot_target.model_id = 'nbso'

    and tot_source.appl_lang_id = 'ENG'

    and tot_target.appl_lang_id = 'ENG'

    and tot_source.type_of_object = 13

    and tot_target.type_of_object = 13

This got my items translated. It worked. I suppose there is no harm in this, is there? 

Hi Tiago,

I think what happened here is that you have attached an Application language and pressed "Generate translation objects” in the Translations screen. The SF will then generate all these translation objects without translation. After that, a Generate definition or Merge base models into work model does not update the translation as the translation objects are not maintained by the base model, but rather by the work model itself.

Probably it is best that we execute the task Merge base models into work model to immediately obtain the Translation objects and the translation from the base model. 

Can you create a ticket for this? Thanks!