Scrollbar thumb is too small about flowless

[Jugen]

Sorry, the VirtualizedScrollPane of Flowless uses an ordinary JavaFX ScrollBar so won't help you directly.

However, having looked at the JavaFX ScrollBarSkin implementation it seems like the simplest option would be to extend it and either override minThumbLength or layoutChildren. The minimum thumb length is currently calculated as 1.5 the width, so you could just change that to a larger more reasonable value in your override.

Then in your CSS file you can apply your custom skin to all ScrollBars with:

.scroll-bar {
    -fx-skin: "my.package.MyScrollBarSkin";
}