It says “double-click to rename”, but nothing happens. Double-click where? On the name? On the colour rectangle? None of them worked.
It is Ctrl+LMB Just forget about that tooltip
Then why does it say “double-click”; is that a bug?
Its a wrong text in a tooltip. I would not call that a bug. That thing is a customization of a predefined listbox element in blender and if I remind correct its simply the default message that comes with it.