When you add a line you need to assign an id to it (the number that you use in the translation file). Just make sure it's something that's not already used and you'll be fine.
Thank you very much! And do you confirm that I also need to edit the dialogue file (for example wilson.lua + wilson.moon) in addition to text_translated.lua? Just wanted to make extra sure so I don't break anything
Yes, you first need to add the line to the game source, and then to the translation file. When added to the source it needs to be wrapped appropriately—for example if Ines says something, it should be something like INES(1025, "This is the text"), where 1025 is the id you assigned.
