Complex sentence: Once the previous 4 S's have been established, they become a new way of working, a new tool or a new output requirement, review the first 4 S's and make changes as appropriate.
Split into simpler sentences: Once the previous 4 S's have been established, they become the new way to operate. When an issue arises such as a suggested improvement, a new way of working, a new tool or a new output requirement, review the first 4 S's and make changes as appropriate.