https://www.yworks.com/products/yed https://www.yworks.com/products/yed Free and easy to use, and has a lot of tricks to e.g. get an uncluttered layout (straigh

https://www.yworks.com/products/yed https://www.yworks.com/products/yed Free and easy to use, and has a lot of tricks to e.g. get an uncluttered layout (straight arrows, aligned boxes,...)