Path Edit mode is when shape anchor points are visible but moving the mouse does not draw anything. In Path Edit mode, you can edit or delete existing anchor points or add new anchor points.
To combine several shapes into one, you can select the shapes and then apply one of the combine options in the Property Inspector to create new shapes out of the overlapping objects.
To draw a straight line, click with the Pen tool () and then move the pointer and click again. The first click sets the starting anchor point, and the second click sets the ending anchor point of the line. To constrain the straight line vertically, horizontally, or along a 45 degree diagonal, press the Shift key as you click to create the second anchor point with the Pen tool.
To draw a curved path with the Pen tool, click to create the starting anchor point and release the mouse button. Move the mouse pointer to another part of the artboard, drag to set the direction of the curve, and then release the mouse button to end the curve.
To convert a smooth point on a curve to a corner point (or vice versa), double-click the shape or path with the Select tool () to enter Path Edit mode. With the anchor points showing on the selected artwork, double-click an anchor point to convert it to the opposite. If it’s currently smooth, it will become a corner point and vice versa.
A UI kit is a file or set of files that contains resources, such as user-interface elements (buttons, icons, and more), that are specific to an operating system. It can help you design apps (or websites) that match a design language like iOS.