Dashboard - how to draw lines?

Hello,

I work on a dashboard. I understand basic html. I like to draw two boxes in different colors on the background. There will be multiple small boxes inside or over the boxes in the background. I defined the large boxes as <div> and the smaller boxes also as <div> inside the larger <div>. So far so good.

How can I draw lines with arrows between the smaller boxes?

Each small box represents a process that gets a number in a circle and a status indicator: green = okay, red = not okay. If there is a problem with one of the smaller boxes, dashboard user should be able to click and drill down to get more info.

The csp page I work on can be found here: https://github.com/oliverwilms/irismonitor

I welcome any help