If an Observing List is set to "Showing objects observed in this list only" and there are no observed items in that list the option to change that filter is gone. Similarly, if an Observing List is set to "Objects not observed in this list" and there are none, the filter option is gone. This was an issue we had some time ago that was fixed (apparently temporarily).
I am on the latest beta version (no update available). 7.4.1.7
(also still waiting on fixes to the multitudes of empty observing sessions too!)
