StereoKit: using a grab bar below the window for movement.

GrabBar.cs

Pose grabBarPose = new Pose(0, 0, -0.5f, Quat.LookDir(0, 0, 1));
Vec2 windowSize  = Vec2.Zero; // First frame will not be in the right spot unless we know window size in advance.
public void Update()
{
	// Use the size of the Window to position it directly above the grab
	// bar. Note that we're using the Pose relative Up direction instead of
	// just the Y axis.
	Pose windowPose = grabBarPose;
	windowPose.position -= grabBarPose.Up * windowSize.y;
	// Begin the window, only show the body, and don't allow the user to
	// grab it. That'd require a bit more work :)
	UI.WindowBegin("Interface", ref windowPose, new Vec2(0.15f, 0), UIWin.Body, UIMove.None);

	// Some UI to fill up space
	UI.Text("Here's a window that can be moved via a bar below the window!", TextAlign.Center);
	UI.HSeparator();
	UI.Button("Testing!");

	// Save the size of the window before ending it. MUST be on a new line.
	windowSize = new Vec2(UI.LayoutRemaining.x, UI.LayoutAt.y - UI.Settings.margin);
	UI.WindowEnd();

	// Show the window grab bar at its own location.
	UI.Handle("GrabBar", ref grabBarPose, new Bounds(new Vec3(windowSize.x * 0.9f, 0.01f, 0.01f)), true, UIMove.FaceUser);
}