With the release of Framework 6.0, you are able to obtain the URL for Portal Documents for a specific subfolder as well as a document. You can then link this subfolder in a Portal Text Editor or List Island to get to that document subfolder more easily.
To do this, you will want to navigate to Portal Documents.
Note the URL at the top of the page is the URL to link to if you want to go directly to the top-level Portal Documents list.
Go to the folder you wish to get the URL for. For example, if I want to get the URL for Training Documents Nathan, then I will click on that folder.
Note the folder we are in, but the URL hasn't changed at the top.
Go into the Properties of one of the items inside the folder by clicking on the item's dropdown, and selecting Properties.
What you do in there or what it looks like is irrelevent. What you want to do is hit Cancel on the Properties screen. This takes you back to the same view we just had, but.....
Note that the URL has changed! This is the correct URL to get to the folder you are currently seeing the contents of. This URL can be copied and pasted into a Portal Text Editor or as the URL in a List Island to access the contents.