Hello!
So I use Kagi on four devices (desktop, laptop, two phones). I made a nice custom CSS that I use on my desktop, which changes the layout slightly and increases the body width and scaling given that I have a large ultrawide screen. However, on my phone and laptop, I prefer to stick to the default Kagi CSS. If I enable custom CSS, it applies to all devices. If I disable custom CSS, it also disables it on all devices.
Today, I opted to inject the CSS on my desktop with Stylus so that I don't have it enabled on all devices by default. It would be very convenient to save devices and toggle CSS on or off per device. I don't think any other search engine has this feature built in, so no one that I know of offers the feature I am suggesting.