To join hardwired (i.e. inwall switches and plugs ect) devices to my HE hub I made a $20 wire harness using clip connectors and a 3 prong cord. The clip connectors make it safe, easy and quick to wire up a device. Now I can discover\join a hardwired device to HE without having to install the device in the wall first. The harness also comes in handy to test automations on a device prior to installing it in its final location. I included links to the parts I used for the project. I hope some of you find this simple solution as useful as I have. Enjoy!
You should join devices "in-place". That way you'll know if they will be able to reach the hub when they are in that location. If you have to bring the device to the hub or the hub to the device, odds are your mesh isn't strong enough to reach the device and it won't work anyway. If you join devices near the hub they will also have to rediscover the best route to use when they are in their final location.
The one noteable exception to this is Z-wave locks. They can only be paired close to the hub.
I have never had an issue with joining in this manner even with outlets ended being installed far from the hub.
The point is, this isn't necessary and can lead to problems, hence our recommendation to always pair in place, with the exception of zwave locks, and even those you should try in place first.
I'll add that it's important to make sure that the device has been reset and trying to join. I had trouble joining my AEON water sensor last night (sensor under kitchen sink, HE in basement beside fuse panel) and was only successful after I brought it down to the basement, but now that I think about it I only figured out how to properly factory reset it after I brought it downstairs (had to hold the Z-wave button for 20 seconds).
With non Z-wave Pro, pair in place never worked for me unless the switch was within 10 feet or so of the hub. I just make a 100ft ethernet cable and walked around the house with the HE to pair all of my devices. And even if you have Zwave pro stuff, if you even have just one non-Pro device in your mesh, the Pro features don't work (like extended pairing range).
Now, my plan is to get rid of all Zwave because it sucks. Already replaced locks, just need to replace a few switches and water sensors now.