Thank you for your question! How are you adding files to Screencast.com?
Unfortunately, if you are using the Web Uploader or the Desktop Uploader, there is not a way to set a default folder to upload files to. However, there may be an alternative that would help to improve your workflow. If you have are not already, you could try using the Desktop Uploader, which allows you to choose which folder your content will be sent to before each upload.
I will bring the default upload feedback back to the team.
Thanks again, and please let me know if you any more questions!