What's new in Xcode 10:
An ability to launch XCTest and XCUITest in parallel, so you can run your test suite on multiple simulators at once. That reduces the test execution dramatically.
xcodebuild enhancements. For example, you can upload an app to App Store from the xcodebuild tool or run control the behavior of parallel testing.
Ability to create custom code snippets for any language and reuse them whenever needed.
Dark mode, which you can switch on from System Preferences. You can also switch your app in and out of Dark Mode while debugging or right in the Interface Builder.
Newly-created schemes are now shared by all users of an Xcode project.
Supports of multi-cursor editing in Source Editor, which allows you to quickly edit multiple lines of code simultaneously.
Default build system activation, where the new build system provides improved reliability and build performance, and it catches project configuration problems.
Source Control workflow enhancements. For example, integration with source code collaboration platforms (GitHub/GitHub Enterprise, Bitbucket Cloud/Bitbucket Server, GitLab/GitLab self-hosted), ability to resolve merge conflicts or create ssh keys directly from Xcode. Also, you’ll be pleased with the improved look of changes highlight with more in-depth information on the actual commit message.
Source Editor in Xcode 10 now supports an overscroll!
Code folding got dramatic improvements with an ability to fold almost anything. Also, using code folding ribbon it’s easier to do it via interface.