You can use this to add a new Rotation command before the currently selected command in a shape's command list. (Position of the command in the list will have an effect on its spatial consequence.) This new command will start out with its parameters randomized, but you can change them to whatever you want.
Each shape in a design maintains a variable-length list of operations in an internal language. This list can be modified in mutation to lengthen, shorten, and recombine with others. These commands are run on each shape as it goes from genotype to phenotype.
The Rotation command rotates a shape in the XY plane. It takes one parameter, the number of degrees of rotation.
Note: AgencyGP's Z dimension is up/down. It corresponds to Maya's Y dimension.