@Greg_E Netbox does an amazing job and helps you make connections. I do have one setup but not listed here, however I don't have it fully operational at this moment. Been running some devs on a true one pane of glass solution such as Grafana or alternatives and how it feeds in. Haven't quite settled on anything though.
For the diagram above, generally I'll start off with the physical topology and I'll make a list of the hops it would take to get somewhere on the network until I reach an ending point, usually the longest route first. Then just create the basic flowchart, create my branches as necessary.
The format of the diagram is made up of the container shapes in either horizontal or vertical title, and I change the colors. I try to start with warmer or neutral colors at the background container and cooler colors in the foreground. Something I learned during early days of HTML/CSS.
The icon packs I used were Cisco, but had overlap from Rack, CAE and Citrix icon packs