The evidence of what NS can do is sufficient to explain my statement (otherwise what you are asking of me is to prove a negative).
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But that is it. The extent to what M+NS can do is demonstrably limited to microevolutionary levels. Showing M+NS to can produce macroevolutionary changes has NOT been demonstrated. That is the evidence.
Yes, I am asking you to prove negative.

I know it is an absurd request, but you claimed:
.the evidence shows that the 'stuff' it can do is limited.
Absence of evidence is not an evidence of absence (assuming that the evidence is absent, which is incorrect).
More importantly, you seem to confuse evidence with physical observation. The two are related, but not the same.
There are few examples of direct observation of macroevolution, but they do exist. I suspect that you will reject them, because they are marginal. But let me ask you this: what kind of macroevolution would convince you? Does it have to be something spectacular, like a transition of a hippopotamus into a dolphin?
Contrary to your other claim, vast majority of research biologists and related scientists consider evidence for macroevolution overwhelming. This is demonstrably true if you do search for peer reviewed papers on evolution in scientific databases. This is not a proof that macroevolution is true of course, but it will show that your claim:
many scientists are very aware of the capabilities of NS and are instead looking for an alternative explanation.
is unsupported. Unless of course your definition of "many" is few.
Also, what is this alternative scientific explanation that they are looking for?
Going back to hippopotamuses and dolphins. They are actually quite closely related. No one will be able to demonstrate to you that transition (or rather transition from the common ancestor) but there is plenty of evidence for that relationship. There is at least half a dozen transitional forms in the fossil record and related palaeogeographical, paleoenvironmental and geochemical evidence. These are not so-so stories.
Tell me, why do dolphins and whales share more DNA with hippopotamuses or cows than cows with horses? Why do whales have muscles for moving ears if they don't have external ears that can be moved? why do they have vestigial olfactory nerves? Can they smell underwater? Why do their foetuses have hair or vestigial limbs?
Can you explain the purpose of all these features? Or maybe you don't believe in any purpose of such things? Maybe you think that animals are just lumps of random organs thrown together, whether they fit or not? Maybe the alternative theory of your many biologists can explain that? Please, share these explanations. Because all these things can be explained by evolution. And all you have been saying so far is that it has not been demonstrated.
Also, can you or your alternative theory explain why humans posses mutated, non-functional genes for production of egg yolk in exactly the same genome location as chickens? Is this a sign that in our "plasticity" we may start laying eggs at some point?
No, you have it backwards. Appealing to your illustration, what I am saying is that we have witnessed the sun existing for the entire course of recorded human history. There is no reason to think that the sun did not exist prior to recorded human history because 1) we have witnessed it existing for as long as we know, and 2) there are not mitigating factors to suggest a change of that status.
1) we have witnessed NS operating for as long as we know, and
2) there are no known factors that would prevent NS from continuing its operation on a larger scale in longer timeframes.
Basically, you are saying:
- "Yes, I believe that 1+1=2."
- "What about 1+1+1+1+1=5?"
- "No, this hasn't been demonstrated!"