Those are called "sequences" in Encounter Test. You can write out the sequences for a testmode as follows:
report_sequences TESTMODE=FULLSCAN format=node
These sequences can be copied to another file and edited as desired. You can then re-build the testmode using these modified sequences. Consult the ET Modelling Users Guide for more information.
FYI, the timing of signals is not defined in the sequence... only the ordering of events. You can adjust the timing of specific signals during write_vectors.
Modifying the sequences is somewhat advanced, and it shouldn't need to be done in normal circumstances. Why do you feel you need to edit the sequences?