By default, Project.el will remember the project directories you have visited. But, sometimes you might want an auto indexing system, similar to Projectile.el’s projectile-project-search-path variable.
Project.el provides some functions for this:
project-remember-projects-under- Index projects under a certain directory. Good for running at startup.
project-forget-projects-under- Unindex projects under a certain directory.
project-forget-project- Unindex a single project.
project-forget-zombie-projects- Unindex all projects that don’t exist anymore. Good for running at startup.