Hi Raimonds 

Thanks for posting in the Community. Yes it's possible to draw a line using just your mouse two different ways:

1. Press the "L" key on your keyboard > click and drag your cursor across the canvas to draw your line.


2. Right-click on your canvas > select “Draw Line” from the drop-down menu that appears.

For more information about how to take the most out of our line features please take a look at our Work with Lines article from the Lucidchart Help Center.