I don't have time to go into more details for the rest of the comments, but this statement highlights misunderstanding of the author regarding the biology of SARS-CoV-2. A furin cleavage site has been identified in other coronaviruses including
MERS and HKU1. Both of those are within the beta coronavirus clade that includes SARS-CoV-2. The finding of a furin cleavage site in other naturally occurring and related coronaviruses that infect humans is not a surprising finding. To suggest it isn't naturally found in other related coronaviruses is false, and to suggest any furin cleavage site is evidence of genetic engineering is not based on any facts.
Science hasn't reached a point in which scientists can string together engineered sequences of nucleotides or amino acids to fully create a new protein. Such a process would take currently years of failed attempts to engineer a protein. If a lab was going to engineer a virus, you would find long regions of the virus that match 100% with other viruses. That doesn't occur with SARS-CoV-2. CoV-2 even has unique sequences, within the receptor binding domain that make it different from the pangolin coronavirus.
Even a 1% difference in nucleotides between coronaviruses is a significant difference. For coronaviruses that means 300 nucleotides are divergent.