I am running an old version of pl/sql dev 5.1.0.654 01.8034. But it has a menu option to view collections while debugging. I haven't been able to get it to work, however. What steps should lead to a view of a collection in a user-defined type?
Just right-click on the collection in the source text and select "View collection". You may want to upgrade to 5.1.6, as there were some collection-related bugfixes since 5.1.0.