How can I create a folder list with subfolders - like windows explorer folders

Question

In addition, being able to collapse the subfolders would be very useful (as windows folder list, and/or mindmap)

Answer 1

yEd supports the concept of grouping. Each group is represented by a group node that may be collapsed or expanded as needed.

Group nodes are available in the (lo and behold) "Group Nodes" palette section.
A set of selected nodes may be grouped using either "Grouping" -> "Group" or CTRL+ALT+G.
New nodes may be dragged from the palette into existing, expanded group nodes.
Existing nodes may be moved into existing, expanded group nodes by pressing and holding SHIFT while moving the node into the group.

Answer 2

Groups can be nested to create a folder hierarchy similar to a folder list.

If you add in some icons (folder-open, folder closed) and some nodes as documents (with a document icon), you can get the effect you want.  Groups in yEd do not keep track of relative positions with neighbouring groups, so a bit of manual tweaking is required whenever you open or close the "folders".  See the folder-example.graphml file.