Current implementation doesn't allow it. I tried the following without any success. We need it in SB.

-fx-size was a possibility but doesn't do the job. By the way -fx-size is not documented in FX CSS spec.

I did the following without any success:
.messages-table .column-header, .messages-table .filler {
    -fx-size: 1;
    -fx-border-width:0;
    visibility:false;
    -fx-border-insets:0;
}

Is there some specific rules?