A modern programming language that makes developers happier.

kotlinlang

I see that intellij idea 2020.1.1 Preview was released. Where can I find the release notes for it?

If you use the Jetbrains Toolbox App to install/manage versions, it will notify you of new versions, provide links to the release notes, and allow you to rollback if there's an issue.

It also allows for installing more than one version of an IDE. Very useful and highly recommended.
<https://www.jetbrains.com/toolbox-app/>

As to your specific question, they put it all in their Confluence. Here's the link for 2020.1 latest builds, so you'll find download links, and Recent Changes Release notes for all versions.

<https://confluence.jetbrains.com/display/IDEADEV/IDEA+2020.1+latest+builds>