Windows Sandbox is a new feature that allows users to execute programs in a sandboxed environment that has no affect on your normal system. Microsoft reportedly made it available in an unlikely place to install the Chromium-based Microsoft Edge browser. The files associated with the Microsoft Edge Insider build will be located in C:UsersWDAGUtilityAccountAppDataLocalMicrosoftEdge folder. Other users who are not part of the test have found that the folder exists, but it is empty.
Source: https://www.bleepingcomputer.com/news/microsoft/chromium-based-microsoft-edge-added-to-windows-10-sandbox/