To reproduce
add a button
go to Inspector and try to paste smth like following lines into first of textAreas of Style editor

-fx-background-color: #ffffff14, #000000cc, #090a0c, linear-gradient(from 0% 0% to 0% 100%, #4a5661ff 0%, #1f2429ff 20%, #1f242aff 100%), linear-gradient(from 0% 0% to 0% 100%, #242a2eff 0%, #23282eff 100%), radial-gradient(focus-angle 0.0deg, focus-distance 0% , center 50% 0%, radius 100%, #878e94e5 0%, #ffffff00 100%);
-fx-background-insets: -3px -3px -4px -3px, -3px, 0px, 1px, 2px, 0px;
-fx-background-radius: 7px, 7px, 7px, 7px, 7px, 7px, 7px, 7px, 6px, 6px, 6px, 6px, 6px, 6px, 6px, 6px, 5px, 5px, 5px, 5px, 5px, 5px, 5px, 5px, 4px, 4px, 4px, 4px, 4px, 4px, 4px, 4px, 3px, 3px, 3px, 3px, 3px, 3px, 3px, 3px, 5px, 5px, 5px, 5px, 5px, 5px, 5px, 5px;
-fx-font-family: "Arial";
-fx-font-size: 26px;
-fx-padding: 10px 20px 10px 20px;
-fx-text-fill: red;


It will not throw any alert dialog of notification, and menu item "Reset to default" accessible from gearbox will be still disabled. And it also will not change anything. I doesn't look as normal behavior.