How to leave a Whatsapp group without informing the entire group?
What you are asking has not been implemented yet.


  How to leave a WhatsApp group without the other participants knowing?


Sorry. They will know when you leave: "Rogério Dec has left the group" will be there for all to see and know.


  Or is there any way to hide the group from the conversation list?


Partially. If you archive the group, it will disappear (actually go to the bottom) from the conversation list. However, when someone in the group sends a message, it will be seen again. Archive it again.