Descript automatically syncs your Projects to the cloud, so you can remove the files from your computer at any point to free up disk space.
To remove downloaded files associated with a Project, click on the Project's "..." menu:
and select "Remove Download."
The next time you open the Project, Descript will re-download the files.
If you'd like to quickly delete all Descript files and preferences stored on your computer, see: How can I delete Descript data/preferences?