Explanation
The Capture All Elements feature is a tool that lives inside Capture Elements from Object Repository, and it extracts all the elements of an application from multiple screens simultaneously using the Computer Vision technology. It adds them to your Object Repository library, so that you can use them in your automation projects without having to manually add them one by one1. This feature is available in Studio and Studio Pro, but not in StudioX2.
References:
UiPath Community 2021.10 Stable Release - UIAutomation.
Capture Elements for Object Repository - UiPath Community Forum.