You can design and create a custom template definition file using a text editor with basic YAML validation. Start with the
Creating Command Central Composite Templates tutorial, which walks your through the steps required to develop a basic composite template.
You can also use the sample composite templates from the
sagdevops-9.x-template-samples project on github as a source template or example for creating custom composite templates. Read and follow the instructions in the
readme file of the project and then select and modify the sample composite template that matches or is close to your requirements.