Currently, Collection symbols cannot be ungrouped. It is possible to modify the collection criteria in order to decide what symbols and attributes to include. But there is no way to revert from a collection and re-use the symbols separately.
The current workaround is to "Modify Collection" -> Copy the content of the collection -> Exit the collection -> Paste the content
It should be natively possible to Ungroup collections as easily as it is to create one.
At this time, this item is not currently scheduled for a release of PI Vision. If this changes, this item will be updated to reflect the current status.
I agree, this would be very helpful.