VirtualFlow has unnecessary calls to addAllToPile() i.e.

    public final BooleanProperty verticalProperty() {
        if (vertical == null) {
            vertical = new BooleanPropertyBase(true) {
                @Override protected void invalidated() {
                    addAllToPile();
                    pile.clear();
                    sheetChildren.clear();

...
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We can replace the addAllToPile with

cells.clear()
pile.clear()
...
...