Setting up a new dev environment

Create a new *.nix file in the shells directory that describes the environment (this is the hard part).
Execute lorri init in the base directory of your project. This will create a .envrc file and shell.nix file.
Edit the shell.nix file to just import /home/charlotte/.local/share/nix-shells/your-new-file.nix
Execute direnv allow to load the .envrc file which in turn uses lorri to load your shell.nix file.