Procedures and Functions cannot be expanded in the Schema Browser, although Packages can.
Is there a reason for this? There is no '+' icon to expand these, unless you click on them first.
It is actually by design that the '+' doesn't show up immediately for procedures.
With packages there's a '+' sign because every package has at least a spec underneath it, so the '+' is there for immediate expansion.
With procedures, Toad would have to parse every one of them to see if there were parameters to show, since not all procedures have parameters.
This would result in a big performance cost, so this is why it appears only when selecting on the required Procedure first, then Toad parses just that object for any sub nodes.