This plugin simply adds a Simple Lit material (SubTarget) to the Universal target for Shader Graph for URP. If Unity ever implements the Simple Lit master node themselves, it should be an in-place replacement for this. To the point where you'll likely even get code conflicts.
Once it's been installed, it should simply be a matter of just making a Shader Graph (there's an option in the Asset Creation menu for SIMPLE LIT SHADERGRAPH, near LIT SHADERGRAPH) and choosing the Material "Simple Lit". Basically the same way you'd make a Lit or Unlit shadergraph, instead just choose Simple Lit.