DDEV will sync your project directory.
You can sync some files into your home directory by symlinking into ~/.ddev/homeadditions or PROJECT/.ddev/homeadditions.
https://ddev.readthedocs.io/en/stable/users/extend/in-container-configuration/
However, if you want to sync a whole directory, such as another project, add a docker-compose.mounts.yaml file:
services:
web:
volumes:
- "$HOME/Sites/mantra:/var/www/html/mantra"Articles