Changing Window Title and Icon

Yes, you can do that with KubeJS too.

To change title, all you have to do is change title in kubejs/config/client.properties.

To change icon, you create a kubejs/config/packicon.png image in standard Minecraft texture size preferably (64x64, 128x128, 256x256, that kind of size).

The image has to be saved as 32-bit PNG, not Auto-Detec/detect/24-bit, otherwise you will get a JVM crash!

Here's how to do that in PaintNET:

Example result: