Your example using Find with unique id, is a good example of the case where the warning can be ignored.
We do plan to allow more flexibility in setting exits which are repetitive by default, such as the <Records> exit of Find, to non-repetitive, It's just that we have not got around to implementing this capability yet.
Even with this implemented there will still be scenarios where flow from repetitive to non-repetitive is intentional.One example is a repetitive element R which may or may not output a result, with flow to a non repetitive element N, The logic here is that N is activated if and only if at least one instance of R outputs a result.
The purpose of Collections/First (and Last) is not to overcome the warning per-se, but will work for you in most cases (not for elements of type Nothing).
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