I have a suggestion. Manipulating sliders to move the mask is cumbersome and not precise. Can enter the option to move the mask in the Mask: Simple Shape function using the mouse on the preview screen?
to have a more finer precision, you can move the mouse pointer over a value (e.g. “Horizontal”, 65,00% <–) and scroll the mouse wheel.
Additionally to scrolling over the value, you can change it by clicking on it and typing a number.
But I also think a rectangle like for the Size and Position filter would be more useful and faster than the current method.