Is it correct and appropriate to omit the second modal verb in the sentence below?
At this scale, objects can be identified and models [can] provide excellent answers.
It is possible, as it is a parallel construction. But it makes it harder for the reader to parse the sentence.
In this case, to avoid complications you can just repeat "can".
You may do this, but it is not advisable because you effectively have a double ellipsis: both "can" and "at this scale" seem to apply to both verbs. Furthermore, the "can" when applied to "provide" is vague. I suspect that what is meant is
At this scale, where objects can be identified, models always provide excellent answers
At this scale, where objects can be identified, models frequently provide excellent answers
At this scale, where objects can be identified, models sometimes provide excellent answers
"Can" may have any of those meanings. Determine which you mean, say that without the vague modal, and be clear.
Frequently, when you wonder whether something is grammatical, it turns out what you are really wondering is whether your thought is clearly expressed. Grammatical English is not necessarily clear English.