During Modify, you cannot change the type, sub-type, or end condition of a feature.
Find/Modify/Suppress/Simplify is not supported for thicken or cavity.
For thin extrudes and revolves, Find considers only the One-Direction thickness. During Modify, only the One-Direction thickness is changed. The second direction is ignored, even if the feature was originally specified with the Two-Direction type of thickness.
Find is not able to find constant radius fillets with multiple radii applied to loops.
During Modify or Suppress, SolidWorks regenerates all features in the part after each modify or suppress. This increases the processing time of these operations.