Starting with Windows 10, version 1809, Windows Preinstallation Environment (PE) is released separately from the Assessment and Deployment Kit (ADK). To add Windows PE to your ADK installation, download the Windows PE Addon and run the included installer after installing the ADK. This change enables post-RTM updates to tools in the ADK. After you run the installer, the WinPE files will be in the same location as they were in previous ADK installs.
Download the Windows PE add-on for the ADK Windows 10 1809
Download the Windows PE add-on for the ADK Windows 10 1903
Here is a PowerShell script from Johan Arwidmark that automates the setup of Windows ADK 10 including the WinPE Addon: