Object Viewing Filter
The Object Viewing Filter is a little button that can be used to restrict the selectable objects based on their Access Mode
It is hidden by default because it is seldom used.
If is is ever needed, it can be unhidden by clicking on the Tools button
and then selecting the item 
It would then appear as the red-circled button below:

By default it is set to U, which is the initial of User and means that only objects with access mode = U are "filtered through", i.e. are allowed.
When clicked upon, a dropdown appears with the available options, as below:

The Object Viewing Filter can be hidden by clicking on the Tools button
and then selecting the item 
