Annex SL applicable to system documentation?

Answer:
The Annex SL structure is only the structure that the international organization for standardization has determined they want to use when they create an ISO management system standard. The standard helps the ISO group to create management system standard that better follow the plan-do-check-act cycle and are easier to integrate with other management system standards since they have many common elements that can be more easily recognized between standards since the clause structure is the same.

This structure is not required, or applicable, to procedures that a company creates for its management system.
To better understand the Annex SL format, see the article: Is ISO 45001:2018 compliant with Annex SL, https://advisera.com/45001academy/blog/2019/03/08/is-iso-450012018-compliant-with-annex-sl/