When there is no header and the graphic is laid out to the left of the content area, the padding of the graphic container that is currently set via modena.css is:

.dialog-pane:no-header > * > .graphic-container {
    -fx-padding: 0.833em 0 0 0.833em; /* 10px 0px 0px 10px */
}

but the right/bottom padding shouldn't be 0, probably the same padding for all sides would be expected.

See attached test and picture.