The line tool can be found in the main menu on the left-hand side of your Cacoo Editor:
Clicking the Line tool automatically defaults to the Straight line, but for more line options, click the arrow.
After selecting your line, your cursor will change into a Precision Select cursor that allows you to click and drag to create a line of any length on the target sheet.
To make your Straight lines vertically, diagonally or horizontally aligned, press SHIFT while clicking and dragging.
Pressing the SHIFT key while creating any other line except for the Freehand line will create vertically- or horizontally-aligned lines when you drag upwards, downwards, or to the side. However, dragging diagonally while keeping SHIFT pressed results in lines that are identically curved.
Styles can be applied to the line before or after you create it. When you select the line you would like to create, the Line style menu will pop up with options to change line thickness, color, style, and type, and also give you the option to apply styles (ex: arrows) to the start and end points of the line.
If you need to find this menu again after creating your line, you can click the Line Style icon in the Toolbar to retrieve it.
The curvature of Curved and Elbow lines can be altered by clicking on the squares that appear when the line is selected.
The “elbow” in Elbow and Elbow rounded lines can be adjusted by clicking the center square with arrows on either side and dragging it from side-to-side.
Editor information before 6/27/18: https://support.cacoo.com/hc/en-us/articles/212778448-The-Editor
Connecting lines to objects
If the object is a Shape, you will see the Shape’s anchor points also become highlighted. These indicate the different points of the shape you can connect the line to.
The anchor point will turn red to indicate that the line has been connected.
If the object is a Textbox, you will not see any connector points. The line will automatically connect to the side of the Textbox closest to it.
After the line is connected, it will adjust accordingly whenever you move the object around the sheet.
Tip: Lines will automatically try to connect to connector points. To ignore connector points on objects, click Ctrl while you drag to create the line. Please note that the line will not adjust when you move the object.