I tried to clean up.
So I went to "Unused Objects" in Object Explorer and selected "Network Objects".
I noticed the following
1) You can't use SHIFT in the list in order to select multiple objects.
2) You can use CTRL but you must take care to not select an already selected object, as it will unselect all other already selected objects.
3) You can't use CTRL+SHIFT obviously to do a multilist-select like you would do for example in Windows Explorer.
4) When you delete multiple objects they show up as having been edited (the pencil appears). However when you delete a single object, it's additionally greyed out.
SC 81.20.9700.646