Windows 10X
Windows 10X is a cancelled edition of Windows 10, a major release of the Microsoft Windows series of operating systems. Announced by Microsoft on October 2, 2019, it was initially developed as an operating system to support dual-screen devices, such as the unreleased Surface Neo. 10X was expected to be released in 2020, but Microsoft later announced that the project had been cancelled in May 2021. However, some features and design changes from 10X were integrated into the newer Windows 11. While the operating system was originally designed for dual-screen devices, Windows 10X shifted its target to single-screen devices in 2020 due to increasing demand for traditional computers from the COVID-19 pandemic. Features

New and changed 
Windows 10X introduced major changes to the Windows shell, abolishing legacy components in favor of new user experiences and enhanced security, as well as some notable design changes, which were integrated into Windows 11:

 The taskbar is now centered. It has 3 different sizes; Small, intended for mouse-controlled desktop computers, and medium and large are intended for touch computers
 The taskbar is automatically hidden, and can be clicked/tapped to be shown. New start menu: Microsoft redesigned the start menu with a focus on productivity, with the search box now at the top instead of in the taskbar like in other editions of Windows 10, as well as a section of pinned apps which is the successor to the Live Tiles from other Windows 10 editions and 8. The Action Center has been renamed “Quick Settings” and given a redesign. Network/Internet controls, volume controls and power options have been moved to Quick Settings. There also exists an area to check notifications and control music playing from a specific app. Window borders have been rounded. The Out-of-box setup has been updated to better fit the new user interface of 10X, with a more modern design, as well as Cortana no longer being an integrated feature. The default UI now uses a more light theme than a dark one. Windows Update improvements: The Windows Update method has been improved to complete faster. Feature updates now automatically install in the background and will only reboot when required to. Enhanced security: 10X introduces a new security system dubbed “State Separation”; instead of installing every file (including the user’s, the system’s, the applications’, etc.) into a single, accessible partition, which allows attackers and malware to easily access system files, 10X installs system, application and other important files into a read-only partition, while leaving the user files in a separate, accessible partition. Therefore, the users and apps can only access files in the user partition. Cancellation 
In May 2021, Microsoft announced that 10X was cancelled, but new features and design changes would be integrated into other Microsoft products (such as Windows 11). References 

Windows 10
Discontinued versions of Microsoft Windows