Hi Dwayne.
I don't think you can change the selectability of a collection in any other way than the outlier.
You can, however, change the selectability of the object in the object properties tab (under visibility). This is exactly the same as unchecking the selectable icon in the outliner.
This makes sense because you don't want an object in a collection changing the properties of the collection itself.
That would be like the child making decisions for the parent.