@pano. hidden folders for plausible deniability is more theoretical than practical. it assumes you are in a worst case scenario where your adversary is sufficiently restricted by rules that they will obey.
you: "there’s nothing on my computer."
attacker scenario a: "administer the shocks on this chump. zap you sure about that?"
attacker scenario b: “we don’t believe you. you’ll sit in confinement until you cooperate.”
will your plausible deniability succeed in such a scenario? most likely not.
others have referenced a scenario where “plausible deniability” is good for crossing borders with sensitive data. however, it’s still a risk for the reasons above. a simpler means is storing data that you may need at a another location in a properly encrypted and anonymized means at a temporary location on the internet. cross the border clean and download the problematic data later. “plausible deniability” no longer required because there is nothing to deny.
the hard reality, as a user that relies on anonymizing software, is that the game is pretty much over if you’ve been located. yes, encryption of the hard drive offers another barrier. but, if it is imperative that you cannot be exploited to give up the decryption mechanism, you should use a method that prevents you from knowing the decryption keys while being able to easily hide or lose the decryption mechanism. one method for this involves using luks for encrypting your hard drive and using a random 8k keyfile for the keyphrase. then, use cryptsetup to gpg encrypt the random 8k keyfile, which will include it in your boot image. you’ll know the passphrase to unlock the gpg encrypted keyfile. but, that passphrase is not what was used to encrypt your hd. thus, lose/destroy your boot key in worst case scenario, and you won’t be able to provide the decryption key under duress. however, this may have the downside of a lengthy incarceration or prolonged torture in worst case scenarios.
tldr; focus less on plausible deniability and more on avoiding practices that will place you in a position to be physically cornered by an attacker.