While we don't have a feature that would let you manually change a student's compliance status in Smart Futures, you can certainly update the PIMS report generated from Smart Futures before submitting it.
As far as tracking those students in Smart Futures, you can use tags to identify those students who transfer in later in the year or in a later grade that would affect the number of artifacts you are required to have for them.
Note - you must be a Coordinator to create or delete tags, but once they have been created for your school, any Instructor or Coordinator can add/remove tags to a student's profile.
Another note - since Smart Futures's accounts can move with a student from one school/district to the next, it would be important to check the completion date of artifacts if you are going by a measure other than the standard. For instance, if you have a student move to your school in 5th grade from another school that used Smart Futures, you may only be required to have them do 2 artifacts for K-5. However, if the student has artifacts associated with their Smart Futures account from K-4, that could affect the artifact count that you expect to see in Smart Futures.