In 12.7.1.11 of Toad for Oracle, clicking "script" tab in Schema Browser for table in large schema, or do "Compare" of "Single Object" for table in large schema across 2 DBs, returns quickly, < 1 sec elapsed time.
Later versions including 12.12.0.39, it's extremely slow, *10 min or more* before returning *identical results*.
The "Scrip" tab can also freeze and cause Toad to crash in some cases.