Microsoft has released a new version 2.2007.9736.0 for Cortana App to Microsoft Store and is available for download, but you can update Cortana manually from the App UI itself, here is how.

The Cortana App in Windows 10 2004 is optional and can be uninstalled and reinstalled whenever you want. Microsoft has made the Cortana available on the Store and pushes new updates to it through it.
Generally, the Windows 10 Apps installed, update themselves automatically if you’ve enabled automatic updates in the Microsoft Store app.
You can also manually update apps by selecting the “Downloads and updates” option in the Store. Now there is a third-way exists, which is updating from the App itself. Cortana in Windows 10 May 2020 Update now supports that.
Update Cortana in Windows 10 2004 In the App
1. Click on the Cortana icon on the taskbar.
2. Click on the menu and select About
3. The App checks for updates and notifies when a new version is available.

4. Clicking on it asks for your confirmation to download and install the update and says Cortana might need a restart.

5. if you click Okay, the update will be downloaded and installed without opening Microsoft Store and Cortana opens on its own after the update is installed. [Thanks to Htnovo].
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