When leaving from work, how to say "see you" to colleagues? Which one is appropriate, "see you all" or "see you everyone"?
From the ones you proposed, only see you all is correct, because "you all" equals "everyone."
Another example would be:
Which equals to:
On the same idea, "I have met everyone" equals "I have met them all."
Interesting question. If you add later (without which, I’m not crazy about either option), then both options are possible, but in different ways:
Here, everyone is a vocative. Compare:
All has a more restricted use as a vocative, for reasons I don’t understand. For instance, Welcome, all! is (for me) ok, but there is a marked contrast between:
Swapping things around:
is sayable (my father might use it), but it is completely impossible to say:
This is part of a systematic contrast:
In short, everyone consists of a (quantificational) determiner (every) and a nominal element (one) and so leaves space other determines (the, you) or other nominal elements (Scots, girls). So, you can’t interpret you everyone as a single determiner phrase. Yet neither can everyone “float” away from a nominal, as all does in You are all nice. So, there’s just no grammatical parse of See you everyone later at all.