Hi all,
HE has what might be a handy diagnostic tool at Settings > Z-Wave Details > Z-Wave Topology, but I can't find any documentation for it. Is there any? For starters, the Blue boxes are the background and the White boxes are my mesh, but a straight line? Hardly real life! What really concerns me are the Red boxes, Red because they're probably bad news. Are they? They are not listed in any of the details, but HE says they're there. Does anyone know of better diagnostic software?
The topology map has been around for ages, just recently did Hubitat add one to it's collection. I think it's that "it's always been around" component that reduced Hubitat's documentation of it...
The Map is all your devices from the viewpoint of what the hub "hears" vs what the devices themselves "hear". Thus the diagonal white line is self-to-self and has no meaning.
The way to read this is to look for any 100% red rows. Red is device can't talk to (or be heard from) the other device at the intersection. A row, 100% red means nothing can hear it when it's sending out packets. That's bad, not much else on the map is bad, though, just all red rows (or columns).
The next thing to look at is symmetricality. For any given row, the column should be the same. If the number of blue in the row is different from the column, then that's telling you that communications will struggle in one direction.
Here's the simplest Map I can find:
Two devices, hub and the device, each able to communicate with the other. 
Here's another extreme example:
The first row AND the first column are all blue, indicating exactly the same as the first example... every device can talk to the hub and the hub can talk to every device. The rest of the Map is redundant. There are alternate paths, great news, but with 100% Direct Connectivity, who cares? (The one red is a battery device that hasn't woken up recently.) Just be aware that it's not "live data". The info could be hours old.
That isn't a Hubitat thing, it is a standard Zwave thing. Silabs PC Controller (Simplicity Studio) which is the base level software have the exact same map.
I personally don't use that map much, it can tell you if something is communicating, but not how well (signal strength, route changes, etc) things are communicating. For that, the main Zwave Details page is a bit more useful, or use the excellent community app from Tony Fleisher that allows you to dig deeper and sort the various statistics. [BETA] A Z-Wave Mesh Tool [C7 and 2.2.4+ Only]
Download the Hubitat app
