Where is Instruments iOS AutoLayout Tool in Xcode 10?

You did not overlook anything! Apple did not release it Yet (Xcode Version 10.2 (10E125)).

You can find new release note of Xcode 10 here, in release notes you can see there is no news about addition of AutoLayout tool.

The Instruments tool that they are talking about in the video has not been released yet (as of Xcode 11 beta 5).

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However, there is already an older Instruments tool which might help you debug Auto Layout on iOS. I tested the tool on an iPhone simulator in Xcode 10.2 and that works. However, I am not sure if it works on an actual device.

Here's how to access it:

1. Create a new Standard > Blank template.
2. Click on the + button > search for the Cocoa Layout template.
3. Once you have the Cocoa Layout template, it is possible to save it as a custom template so that you can access it directly from Custom > Your Template next time.

There is an old but nice tutorial for this tool here.