Anything listed at https://en.wikipedia.org/wiki/Graphical_widget#List_of_commo... does count as "standard widgets". There may be variations in different GUI libraries, but anything that deviates too much from common user expectations will be perceived as broken.
There are ways to avoid traversing the whole volume in each use, namely caching each directory content when it's updated.
As for always showing unwanted information, an interactive solution could allow an option to "fold and hide" specific folders so that their contents are not shown until the user specifically reopens them. A user-friendly interactive solution doesn't require the user to remember and choose among all the available choices for each use, it provides good defaults and reminders on how to access alternative options when those are needed.
There are ways to avoid traversing the whole volume in each use, namely caching each directory content when it's updated.
As for always showing unwanted information, an interactive solution could allow an option to "fold and hide" specific folders so that their contents are not shown until the user specifically reopens them. A user-friendly interactive solution doesn't require the user to remember and choose among all the available choices for each use, it provides good defaults and reminders on how to access alternative options when those are needed.