Similar to creating a custom circle, but with the ability to specify what percentage of the circle to draw. For example: 50% would be half of a circle.
Add an option to the "custom circle" diaglog that lets you toggle on/off semi-circle. When on, there should be a slider for selecting what percentage of the circle to draw, and a progress showing a preview of what you are doing:
<progress class="circle large" style="mask-image: none; transform: rotate(90deg);" value=60 max=100></progress>
For drawing on the layout:
const arc = new Graphics();
arc.moveTo(100, 100);
arc.arc(100, 100, 50, 0, (0.6 * 2) * Math.PI);
arc.lineTo(100, 100);
arc.fill({ color: 0xaa00bb });
//arc.stroke({ width: 1, color: 'white', pixelLine: true });