I've managed to create a connector device (the highlighted one):
that doesn't appear in my global variables:
I believe I did so by choosing a connector device that was not in the value range of the current value of the global variable.
I am unable to delete the connector device - it wasn't available in the delete list, nor did deleting the global variable remove it. Is there anyway to do so without restoring from a backup?
Delete the GV. Then recreate the same GV, and create a Connector for it. At that point you should be able to delete the Connector device. Having an extra connector device around won't hurt anything.
Another way to do it would be to remove the Rule Machine Connectors, which would remove all of the connector devices. Then you'd have to recreate them all.
This worked, thank you - but didn't for me the first time. I recreated the global and gave it the connector type I wanted (which was different from the existing one) and it just created a second device alongside the first.
However, creating the global variable again, and then a new connector with the wrong connector type (this time with an acceptable initial value for the GV) matching the one I couldn't delete, allowed me to remove it.