Would anyone besides me find this attractive and useful in a cluttered project-in-progress?
 
The suggestion is to that each project would get its own folder in the Browser, perhaps getting it's own Tab called "Sandbox" or "Project Folder".  It would be a folder that could contain any dragged-and-dropped MIDI and audio clips from said project.  Contents are saved within the project, but only for that project.  It could even go a step further to be place to drag-and-drop VST/VSTi presets, FX chains, etc.
 
This would be different than just creating a "sandbox" folder in Windows Explorer to be mapped/used in the Browser.
 
Actual contents (i.e. the physical MIDI/audio files) would be saved into a separate folder within the per-project audio folder.  It could be called TEMP_FILES or SANDBOX_FILES (or whatever!) and reside next to the Audio folder.
 
I would find this useful to help me organize a cluttered project, bulldozing away but saving various MIDI sequences and recorded sounds particular to the project that I want to keep and place in the composition somewhere else.  Having an offsite location for the clips could save time by avoiding the juggling of clips as the composition is built.

Maybe something like this already exists and I haven't found it yet.