Version 2.2 Released. Includes all DLC options with an installer script for FOMOD/NMM. See change log for info on other changes.
Version 3.0 Released. Includes all DLC options with an installer script for FOMOD/NMM and MCM configuration. See Below. Requires a Clean Save due to properties added to the Quick Stash Key.
Version 3.1 Released. Clean Save not required to update. I recommend updating now. See change log.
 

 

 
How to do I use it?
Simply drop the the Quick Stash Key* into any container for quick storage of excess items.
*not an actual key, but can be found with your miscellaneous items. 
 
What exactly does it do? 
Simply put, it's the one-click answer to unloading items.
More precisely, form lists are used for removing a number of items quickly into the container (List 1 Items),
then your inventory is scanned to remove further items that are not marked as favorite or equipped (List 2 Items).
After items are removed, then more form lists are used to return any items that should remain in your inventory (List 3 Items).
Since items of the miscellaneous category are not scanned miscellaneous quest items, gold and lock picks are not removed from your inventory.
 
List 1 Items:

• All recognized Books (excluding known quest items)
• All Raw Food (because you normally eat the prepared food.)
• All ingredients (because you're out hunting treasure not making potions)
• All crafting materials (do you see a tanning rack or forge nearby?)
• All Soul Gems (empty ones will be returned as part of list 3)
• All Animal Parts (because troll skulls are heavy)
• Miscellaneous Clutter (why did you pick up that embalming tool anyway?)
• Coming Soon! All of any item you choose (excluding player made potions and player made enchanted items.)Version 3.0
  

List 2 Items:

• Ammo
• Armor
• Potions/Poison/Food
• Scrolls
• Weapons
  

List 3 Items:

• All Known Quest Items
• Empty Soul Gems
• All of any item you choose.* Version 3.0
• One of each item you choose.* Version 3.0
  * will not work for potions crafted or items enchanted in game.
  

Is there more?
Currently the features described are part of the version 1.0 basic package and does not recognize items from DLC. Future plans in this order:

• DLC aware versions (Easy peasy. I just wanted to cover Non-DLC version first and not have to rip out DLC content) Done! Version 2.2
• Basic Configuration for User-Defined List 1 Items. (basically you drop the key, which opens a container. Whatever you put into that container goes on the list.) Skipped in Favor of MCM Menu.
• NMM/FOMOD Installer Script (I could use some help with this.) Done! Version 2.2
• MCM Configuration (in the event that prior goals are met and users request more customization)Done! Version 3.0
  

MCM Configuration:

• Made and tested with MCM from SkyUI version 4.1.
• Stashing of predefined items,described above, can now be disabled.
• Adds user-defined lists that can also be disabled:
  
  • Stash All List
  • Keep All List - Returns ALL items in this list after stashing.
  • Keep One List - Returns one of each of the items in this list after stashing.
    
  
  
  

The first 128 items in the user-defined lists can be viewed and removed individually. There is also the ability to clear each list.

NOTE: To anyone who wishes to modify the 3 configuration formlist outside the game, you will have to use the MCM Options Menu to clear the list you change for it to display correctly, unless you do so before you use it the first time.

Acknowledgements:
krysalynne - for volunteering for and writing the installer script.
various members of the bethsoft forums - for the input and suggestions given on my thread Handling Inventory Items.
The TES5Edit team - for TES5Edit
matortheeternal - for Automation Tools for TES5Edit and for his help in the forum page.
The SkyUI team - for providing a fantastic UI and the MCM menu system.
And Bethesda - for... You know.
....