With the Social tools extension, you can easily access hidden messages from social networks.

The extension itself is not hidden; it's a simple add-on and you can install it by downloading.

If you just want to use the Unseen feature, you can use this extension:

Features:

Block sending "seen" indicator: you can read the message without sending any mask as read (This is also called unseen message).

Block sending typing indicator.

Block "seen" stories FB/INS: you can view your friend's stories free, nobody knows you've seen that.

If you want to add your social account (Facebook, Instagram, or others), you can open the page, click "Add account", and you will be redirected to a page with the list of your accounts.