This would appear to be an obvious strawman. The real “objection” would appear to be not that “we cannot observe its direct action”, but we don’t even have a hypothesised mechanism for this action – making it impossible to test for the existence of this interaction even indirectly.
Lacking even a hypothetical mechanism for how this (purely hypothetical) mind acts on the target that it is supposed to “arrange parts”, this claim (I wouldn’t even call it a hypothesis), is clearly utterly useless for science and is a very weak argument against a set of mechanisms that have been hypothesised, observed, tested, and studied in great detail.
A useful analogy might be the claim that it is fairies (or the Earth’s magnetic field, if you wish for a non-supernatural hypothesis), rather than internal combustion, that make car engines work. You don’t need to directly observe fairies (or the Earth’s magnetic field) doing this to test this hypothesis, but you do need a hypothesis of how the fairies (or the Earth’s magnetic field) do it. Otherwise you’d have no idea what indirect observations would tend to confirm or disconfirm the presence of their action.