+1
Other media players now have UIs which do not break FSE mode.
It is annoying when something bumps the mouse and FSE mode deactivates because the JRiver UI is being drawn.
The way that the remote-controlled UI is drawn in JRiver is non-breaking, so a mouse-controlled version of that could work:
A skinnable UI with a full-width seekbar along one edge of the screen, with playback info and controls on the other. Think iOS video controls.
Hide/show this UI by hovering over either edge, or tapping the screen.
Now it is two features in one: FSE-compatible playback controls, and a new touch-friendly UI.
Have you tried the 10-bit Display Support Test? It could be that you won't see much difference with 8-bit dithered vs 10-bit and can then use Windowed Overlay instead if you have an Nvidia or Intel GPU.
JRiver's existing transparency effects are incompatible with Overlay Mode and the option to disable transparency over movies does nothing.