The current implementation of the draggable scrollbar has a few quirks.

1. The longpress gesture takes 500ms (since that is the default for flutter). But on native it seems much faster, almost instant even.
   From my testing it seems that the value should be somewhere between 50 and 150ms. It might even be that it just differentiates between a drag and a tap down.
   I was able to change this value by adding a deadline field to the constructor of LongPressGestureRecognizer which I set to the values 50-150.

2. The current implementation also has a drag from the right gesture, I haven’t been able to reproduce this on a native iOS 13 device. Even with my apple pencil on the iPad pro it does not work. However, on the sim it ‘seems’ to happen. This is possibly just because the long press gesture is so short and thus already detected which gives the impression of the drag from the right working.