You need to nest it in the /layouts/ folder if you're trying to override or create a new layout -- /custom/layouts/home_-_particles.yaml -- if that doesn't work (TBH I wasn't aware you could override a Layout -- and it definitely won't automatically show up in an Outline you've already created; you'd need to use the Load button to reload the Preset) try copying it but renaming it "home 2" or something and see if it shows up in your Load Presets list.
(personally, when I want to add a new Section for a given Outline I just edit the layout.yaml file that's in /custom/config/outline-name/ directly)
Also, don't try and statically assign Particles to your new section... those numbers after heading, stores, image, etc are unique to specific particles and you should let Gantry write those IDs for you when you drag/drop in Particles. So just create a blank Section under layout:
and you also need to add your new section the structure: area beneath that
docs.gantry.org/gantry5/advanced/creatin...ut-presets#structure
below:
type: section
attributes:
boxed: ''
class: ''
variations: ''
Indentation matters in YAML, so make sure each line is indented properly