This is something that was working on my Gramps 5.1.5 version on Windoze and has suddenly stopped. The first suspect was a recently updated add-on. (Since the add-on redefines the Context Menu and might have adjusted the parent CLI window instead of the spawned Gramps GUI window.) But I have removed the whole Plugins folder from the Gramps51 subfolder of my Gramps User Directory . The problem persists.
I can no longer use the right-click context menu (to mark and copy the logging content of the Windows Command Line Interface window) while Gramps is running. The menu is completely gone.
This occurs both when launching from the Gramps console icon or opening a CLI window, changing to the Gramps folder and calling the Gramps.exe application file. (I had a couple spontaneous exits and was hoping to capture an error message in the log.) After Gramps closes, the context menu becomes accessible again.
(There are a few extra non-critical messages due to moving the Plugins folder:)
Could some other users check their Windows, Linux & Mac versions and see if their Context Menus are available in the Command Line Interface?