The 2018 DEFUSE grant proposed to modify a bat sarbecovirus in Wuhan by adding a furin cleavage site (FCS) in a reverse genetics system of such a virus.
SARS-CoV-2 emerged in Wuhan with a furin cleavage site and a pattern of cutting/pasting sites in its genome, sites modified by a hotspot of silent mutations bioengineers like to use, consistent with a reverse genetics system made by enzymes used in a 2017 paper by several authors of the aforementioned grant.

FOIA’d drafts of this grant also contained more specific plans - designating the specific location for the FCS insertion between the S1 and S2 subunits of the S gene (the same place the FCS is found) and including order forms for one of the aforementioned enzymes hypothesized to have been used to synthesize the reverse genetics system that caused a pandemic.
Additional facts relevant to lab origin theory include:

