Android - How to make a contacts group invisible to whatsapp is it possible to create a contacts group in my Android that wouldn't be visible even to whatsapp "show inivisible contacts" ?

I mean, I don't want that group to appears in whatsapp what-so-ever

If not, is there any app that can easily hide (ie, remove a group from Android contacts) and unhide whenever you want?
The question is not specific hope so. Do you want to hid yourself from certain friends who are in your contact list?

If so, then you can add them to block them in the block list. (But you will be still receiving the messages from them).

Or change your privacy settings in whatsapp according to your convince.