This GitHub Action generates the SAMM toolbox spreadsheet based on the core model.
If you're looking for the spreadsheet itself, you'll find the newest version at https://github.com/owaspsamm/core/releases/latest.
The action is called by the core model build process. It expects the updated model files in the /github/workspace/model directory of the runner.
It loads these files, opens the "dummy" spreadsheet located in the resources folder in this repository and replaces the relant content. In the end, it stores the updated spreadsheet under /github/workspace/SAMM_spreadsheet.xlsx on the runner where it's taken by the parent build process to be published among the release deliverables.