Your quality management system is evolving to include occupational health and safety and/or the environment. In this context, you need to update your existing quality manual to take account of the new standards and, above all, the changes involved (policy, organization, processes, etc.).
In another case, the three management systems coexist and there are several manuals describing the organization of each system: quality manual, environment manual and/or health and safety manual. In the interests of simplification and consistency, you would like to integrate the three systems into one, and merge these documents into a single document: the integrated management manual, for example.
Or, quite simply, you are embarking on a process of structuring your existing system by taking direct account of the three dimensions of quality, safety and the environment, with the aim of obtaining QSE certification.