Microsoft has released Windows 10 Insider Preview Build 18999 (20H1) to Insiders in the Fast ring. This build brings the ability to move and resize Cortana s window to all Insiders. The notable changes found in this Insider build are detailed below. An issue was fixed that caused SearchFilterHost.exe to use a lot of CPU when in battery saver mode. Other notable issues and changes: Fixed an issue that caused the Settings control panel to not launch.Fixed an issue where downloaded theme packs would not properly install.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-insider-build-18999-gives-all-insiders-a-resizable-cortana/