The vast complexity of living things proves that God exists (proof 1)

[Angrboda]

In your OP you assert that a kind of complexity is a reliable indicator of design. This may work for books, computers, and perhaps Clovis points. However there is a large class of very complex objects for which this claim cannot be confidently asserted. Human beings (and for that matter, most of life) are incredibly complex, yet it is not known whether they are the product of natural processes or design. Because we have a huge class of objects which have the property you claim is indicative of design, but we don't actually know whether they are designed or not, your claim that you know that complexity is a certain guide to design is simply false, since you don't know this to be the case for a large, common, and plentiful class of objects (humans). It is possible that they are designed, yet, because it is not known that they are designed, it is not known to be a reliable indicator of design for those objects (humans). If you have independent proof that humans are designed, this argument you've made becomes superfluous to that proof.

Assertion refuted. Complexity is not known to be a reliable indicator of design.