RE FOLDERS: Nope media room just displays everything you import.
You can show/hide different media
types by toggling off/on the media types icons (videos, images, audio) at the top of the window.
If you want to move everything you've imported into ONE folder you have to use
Pack project materials.. under the
File menu.
IMPORTANT: Be careful about duplicate filenames.
I recently had a scenario where some pictures I had imported pictures from various folders had the
same filenames.
This resulted in pictures I had already used in my slideshow being replaced with the duplicates without me noticing until I had produced the project.
I only noticed because the new pictures were stretched so stood out.
This was because they had different dimensions to the ones they had replaced however the slideshow kept the dimensions from the
old pictures resulting in the wrong aspect ratio being used.
Took me awhile to track down what was happening as initially I though it was a bug in PD making the aspect ratio go haywire until I tracked it down to duplicate filenames!