GridPane and other layout panes stores the layout constrains as client properties but it's not possible to change this layout information via a CSS style sheet.

An example:

    Label labelNode = new Label(label);
    labelNode.getStyleClass().add ("input-label"); // All Labels which are "connected" to Input fields
    GridPane.setConstraints(labelNode, 0, row);
    GridPane.setHalignment(labelNode, HPos.RIGHT); // Labels should be right to the next field
    
    TextBox textNode = new TextBox();
    GridPane.setConstraints(textNode, 1, row);
    GridPane.setHalignment(textNode, HPos.LEFT); // TextBox left to the previous label

Now I (or a customer) want to change the right justified labels to left:

.input-label {
  -fx-node-halignment: left;
}

best regards, josh.