Is anything missing in this sentence?

It is wonderful what you can do when you have to.
I guess something is missing between "It is wonderful" and "what you can do" in the sentence above. Right? Its meaning is not quite clear to me. Anyone to explain? Thanks.

<<It is wonderful what you can do when you have to. >>

There is nothing missing here. It means: "It's wonderful what things you can do when you have to." Hope that helps.

Still not quite clear to me. Can you paraphrase it in different words?

It's grammatically correct. That's how I'd say it. (except I'd say weird or something instead of wonderful)

The sentence is grammatically correct, but I think my preference would be for "amazing" rather than "wonderful".

Grammatically, "it" is being used as a dummy subject here, introducing the noun phrase "what you can do when you have to".

Would you plz give me an anlysis of the sentences, Skippy? What does "it" refer to?

If "it" is a dummy subject, then the sentence can be written as "what you can do when you have to is wonderful", right? But it sounds so awkward.

I have the feeling that the sentence pattern "it is wonderful/surprizing/amazing/fantastic/certain/impossible that" should be followed by a clause, not a noun phrase. Right?

<<If "it" is a dummy subject, then the sentence can be written as "what you can do when you have to is wonderful", right? But it sounds so awkward.>>

Exactly. The dummy subject is used here because the sentence sounds weird without it. As a native speaker, the rewritten sentence strikes me as completely unnatural, and in fact I think it loses its meaning.

<<I have the feeling that the sentence pattern "it is wonderful/surprizing/amazing/fantastic/certain/impossible that" should be followed by a clause, not a noun phrase. Right?>>

If the adjective is followed by "that", then yes, it would have to be followed by a clause.

<< It is wonderful what you can do when you have to. >>

Translated:

Necessisty is the mother of invention.