One of the people in the office, who is in the group jira-administrators, and also in a group we created called structure-administrators that should have free run of Structure, created their first structure today. I was helping them go through the steps, and they first added a synchronizer for subtasks (successfully), then went to add a sync on a filter. However, when they click on the "select" link to select the filter, it pops up the "you are not authorized, please log in with an authorized account" window. It's his structure, and he was able to add the sub-task sync with no problems, so what permission is needed to select a filter? No one else has seen this (though only a couple folks have created structures so far).
I did have them create a filter specifically for this structure, so I know they can create and access filters, too.