Hi Mark, thanks for your help.
Regarding the second controller, which doesn’t offer labels or nodes, I think I have missed the obvious - this controller doesn’t have any agents, so I guess it is reasonable that none are offered.
Regarding the ‘production’ controllers that my first question was about: I am using Edge and Chrome, both browers do not show the Label and Node trees.
It seems, from your latest reply, that the Jenkins version is not the reason. But, anyway, I am using the LTS, which is much earlier.
I have another unresolved thread that questions why the snippet generator is not working for me for some plugins.
Snippet Generator not working - Using Jenkins - Jenkins
Perhaps the two problems are connected?