Thank you for this update.

I reached out to Kathy Lee and she helped me solve this. Here's what I did:

I uninstalled the latest version of CubeMX and installed version 6.2.0; It seems like RT-Thread Studio only supports from version 6.2.0 and below.

Hopefully, there would release the support for newer versions of CubeMX soon.

Hope this helps someone.

{{CubeMX now works.PNG(uploading...)}}