Social Security Disability Insurance Return to Work Act of 2019 This bill (1) directs the Social Security Administration (SSA) to establish new disability classifications under the Old Age, Survivors, and Disability Insurance (OASDI) program; (2) limits OASDI benefits with respect to individuals for whom medical improvement is deemed likely or expected; (3) requires the SSA to establish a process for such individuals to return to employment and receive an adjusted benefit amount; and (4) otherwise modifies provisions related to OASDI benefits.