Fuse version 1.7.2 (build 15505)
Windows 10
Open/Create a project -> Click on Menu Items: Viewport -> Device -> Customize…
The application just crashes, no message, no warning, just disappears of the process stack.
Do you have any other details to share about your system?
That menu item should open a .json file in a text editor. Do you have Sublime Text installed? Do you have a default program set to open .json files with?