It'll be great if we could have a Bookmark Panel right below the Folder Tree Panel on the left hand side of the Xplorer main window. This will provide convenience in accessing our bookmarks quickly.
I have drawn an illustration with Photoshop to help visualize my suggestion. Please take a look.
How is this any more faster than the existing solutions?
1. Drop down list
2. User defined short-cut keys
You could have a toolbar just for the first ten bookmarks in your list.
In x2, go to "Customize" -> "Toolbars" -> "Add new...". In there, create a new toolbar. When finished, you will have a new toolbar available in x2. If you r-click on this new toolbar, you can add what you want. The first ten entries in your bookmark list will be available for this new toolbar.
If you store bookmarks (*.lnk files) in a "bookmark folder, you will get practically the same thing (but rather than a tree, you get a limitless list of bookmarks.)
You can create subfolders to store interrelated bookmarks.
The tree on the other hand is confusing because it shows the actual paths for its nodes. It may look good if the nodes are named after conceptual names. In that case, having subnodes makes sense too.