ScrollPane JavaFX make it scroll more?

You could do this in the FXML styling.

.scroll-pane .scroll-bar:vertical {
-fx-unit-increment: 5 ;
-fx-block-increment: 5 ;
}

.scroll-pane .scroll-bar:horizontal {
-fx-unit-increment: 5 ;
-fx-block-increment: 5 ;
}

Play around with the unit and block increment numbers until you get a desired effect.