ISO 45001 - identifying internal and external issues

If your organization uses the SWOT analysis already, then the strengths and weaknesses of the SWOT analysis are applicable tot eh internal and external issues in ISO 45001 clause 4.1. Likewise, the issues causing the threats and opportunities would also be external issues, and the threats and opportunities would be applicable in clause 6.1.

It is however important to note that a SWOT analysis is not a mandatory requirements of ISO 45001, and is only one way to identify this information.

You can learn a bit more of how SOWT works in the OHSMS in the article: Benefits of SWOT analysis in ISO 45001, https://advisera.com/45001academy/blog/2019/05/27/iso-45001-swot-analysis-what-are-the-benefits/