You can select a few blocks, then with the radial menu group them.
You can turn a group into a device using the radial menu.
Sometimes a group is so good, you want to give it a name, a thumbnail and share with everyone to use. You can even sell your devices for Vibz.
A group is more local to a world, and mostly used to organize things in your world into layers.
Groups can be nested inside of other groups.
Using the "eye" icon
At the moment most comfortable way is via the patch web portal portal.patchxr.io
Tip:
A group, and therefore also a device will need to have a block called a Device Landmark inside of it. This will act as the point of the device that will snap to the grid when someone would try to position the device, or group. If one is not there when you are making a group, Patchworld will create one for you so you do not need to remember to create them, however, if you want the anchor point of the device to be in a specific spot, you would want to make a device landmark and position it before grouping.