In my version (28.13) the switching of kernels is synchronized between the Kernel Editor and the Render Settings. The only thing is, that when you connect a new kernel type to the Kernel Output node, it doesn't immediately switch in the Render Settings - you need to click somewhere and then it updates. Maybe that could be optimized.
But one thing that should be changed is, that when you open the Kernel Editor for the first time, the active kernel isn't active in the editor and thus not showing. That should be fixed. At least it stays there once it was selected, unlike the Octane Composite and the Octane Render AOV windows which always loose their focus when you switch out and back in. A long-standing bug.