How to create a new section in the Gantry Joomla template?

Go to templates\g5_helium\custom\config\<default or 12 see this unique ID from template styles->edit->Outlines at top right>\ index.yaml
In index.yaml :
Under sections: add a section unique name and perspective title like the following:
sections:
custom1: Custom1

In layout.yaml:
Under layout, add the layout's unique name with the following format, /layoutuniquename/: { }
Like that:
layout:
/custom1/: { }