Why doesn't VeraCrypt support having more than one inner volume, each having its own password. It seems to me that someone could always use extortion to reveal the inner container password in addition to the outer one if they knew VeraCrypt well and how it works. By having more than one inner container you could even have a very small one with a special file in it and nobody would ever know how many inner hidden containers you have, so it seems to me that would be adding an extra layer of security. Comments welcome.
in you question concerning multiple inner hidden containers - you wrote
nobody would ever know how many inner hidden containers you have,...
That would be unnecessary overkill because you may not know one-day either :). Could happen if you are really such a security minded person. And then what?
Say you already have an encrypted veracrypt volume/partition, etc. Adding a hidden volume requisite you create an outer volume in which to hide it. That means you must have several headers for veracrypt to determine where each volume begins/ends; no problem here since the wizard does the calculating for you but have your paper and pencil at hand. It becomes a juggling act remembering how big, where is what, which password to use, how many volumes did I create, etc..- when creating even multiple volumes in which you can create hidden volumes!!
Getting back to my scenario above... I would have two headers from which veracrypt can work with. It becomes even more complicated – in terms of security/secret – since each password muss be strong and unique! I can manage keeping 5 STRONG passwords/phrases in memory without writing them down but more than that requires physical notation because of their infrequent usage, and that becomes a security issue – where to store them. Albeit, the best passwords are the ones you can't remember - I am borderline!!
You didn’t mention how many inner volumes for each hidden veracrypt volume but more than one would set the stage for a chaotic scenario as mentioned - above. It would be like the concept of the Russian Matryoshka doll of nesting 7 in one. Adding the option of multi-inner hidden volumes (if at all practically possible) and you have utter chaos in the making!!
The challenge of already providing a user-friendly application and retaining the atrributes of confidentiality, integrity and availabilty would be totally thrown out of the window if such complexity was added to an already workable solution!!
Besides a hidden volume is a hidden volume without dressing veracrypt up like a Russian Matryoshka doll. Veracrypt allows that much TODAY and you have a better overview of what you may have just done.
And if you follow instructions carefully, according to VeraCrypt,
Even when the outer volume is mounted, it should be impossible to prove whether there is a hidden volume within it or not, your data should be well hidden.
That is my unprofessional thought on the matter.