If you go to Tools > Browser Folders, you can rearrange the default folders in any way you like, show or hide folders, create your own query based or static folders, and create sub folders.
This sounds like a local problem you're having, as my packages within a single schema are always sorted alphabetically. I think you'd have a riot by all users if they weren't!
Is it possible you're seeing packages across multiple schemas and you want them sorted alpha but ignoring the schema name?
For user-defined folders you define the sort order in the query definition.
For system folders the sort order is defined by the current browser filter. Just like user-defined folders, each filter has a where clause and order by clause that is applied to each system folder.