There's not much of an ecosystem for multiplatform yet for desktop projects at all. For macOS you have a way of "making a framework you can use" and that's about it.
There is a lot of promise, though, in the mobile space: https://touchlab.co/touchlab-square-kotlin-multiplatform-col...
My sense is that as the mobile multiplatform space gets ironed out, the desktop space will benefit.
Though generally speaking, Kotlin/Native has a _much_ lower level of "institutional" risk, since the Kotlin approach doesn't subvert the control Apple or Microsoft have over their platforms. Flutter, on the other hand, seems to abstract it away.
Its also pretty slow compared with other native solutions.
If you want a debugger you need CLion, though. And the compiler is really, really slow – but they seem to be working on benchmarking things recently, so presumably it will be improved.