Modify files "flows.json" and "settings.js" in scripts/conf to customize the node-red content. Nodes to be preinstalled could be placed in the snapcraft.yaml file.
sudo chmod 777 -R *
sudo snap install multipass
sudo snap install snapcraft --classic
snapcraft
sudo chmod 777 -R *
sudo snap install lxd
sudo lxd init -> confirm all defaults
snapcraft --use-lxd