You can reset kOS Studio by deleting the data directory. Here are the instructions by OS:
For Linux
To reset kOS Studio from Linux, remove the data directory located at ~/kosStudio/data.
For macOS
To reset kOS Studio from macOS, delete the ~/Library/Application Support/kosStudio folder.
For Windows
On Windows, the data directory is located where you set it during installation, typically at C:\users\<username>\kosStudio. To reset kOS Studio, delete that folder.