I believe that the GENESYS negation tool must get the S-parameter data to be negated from a disk-file (.s2p). It would be nice if the negation tool could extract this S-parameter data from another GENESYS schematic. Hence, one could negate a part that is being dynamically modified (rather than having to repeatedly export the part's S-parameter data to a file).
The new version of Genesys stores the results of all simulations in Datasets in the workspace, which can then be referenced by any part that uses S-parameters (not just negations). Note that the data in a dataset can be exported to an external S-parameter file, which can be used in other workspaces as well.