DEX associated the following file extensions.
.project - used for project files.
.part - used for part files.
.art - used for art files.
A default program is the program that Windows uses when you open a particular type of file, such as a music file, an image, or a web-page. For example, if you have more than one web browser installed on your computer, you can choose one of them to be the default browser.
How to Change File Associations in Windows 10
Right-click the Start button (or use the WIN+X hotkey) and choose Settings.
Select DEX from the list
Choose Default apps on the left
Scroll down a little and select Choose default apps by file type
Locate the file extension for which you want to change the default program
