So, you’ve generated a shape key, but now you want to separate that shape key into 2 or 3 unique shape keys? Yea, the only way to do that is to manually re-create those desired results with time and effort, or you can just learn about this addon that solves this time-consuming issue.

Vertex Shape Keys solves the problem of grouping shape keys. Group shape keys lets you generate sets of Vertex Groups of your choosing. In other words if you have a 'smile' shape key, and a 'Left Face' and 'Right Face' vertex groups, you can automatically generate a 'smile for Left Face' and 'smile for Right Face' shape keys.

If you have to make changes to the Smile shape key, you only have to change the original and generate again.

Master Shape Keys includes all the mentioned above and everything else. With it you can combine shape keys which simplifies the process of utilizing more than 1 shape key to be activated at the same time.

With Additive Off each shape key is activated and closed consecutively, each next shape key activating when the prior shape key starts to close.

With Additive On the process is similar, but each prior shape key after reaching full extension remains open and doesn't revert to the original value, unlike with Additive Off.

The opportunity for more expression and control over a character’s face or a mesh’s form becomes a reality, not to mention the prospect of comedic over-expression that’s easier than ever!

Using Sync Object, you can select another object with shape keys and will have the option to sync to a specific Shape Key, which will make the targeted shape key affect the object you've chosen.

Bake Merged Keys for exporting to alternative engines (Unreal, Unity), or for use within Blender, without the MSK addon, while preserving animation data. Additionally, they can be utilized on render farms.

Organizing shape keys is a nightmare because you just cannot give them structure due to the lack of any such mechanism in native Blender.

This is where Shape Key Collections saves the day and allows for full control over your shape keys. Bring structure to the chaos, a folder structure, that is.

With this new management system you can rename and organize which shape keys go in which folder collection, including the benefit of subfolders for full detail of your many shape keys.

Did you know you could set up shape keys to be driven by bones through an automated process via drivers on a 3D UI? It can work on any model or mesh, including facial shape keys of any character. This is all possible with the epic addon Driver-Rig - https://blendermarket.com/products/driverrig-shape-keys-bones

Want to get Master Shape Keys with Driver-Rig as a bundle for a lower price? Why not - https://blendermarket.com/products/driver-rig-msk-bundle

Release Notes

Version 3.8

• Adjusted the ‘min/max limits’ of combine keys from a min of 0 to a min of 1, since having it on 0 would result in shape keys that do nothing.
  
• Added the ‘bake merge keys’ ability, which lets you bake the animation of shape keys driven by merge keys to preserve the animation data when exporting the model to other engines (such as Unreal) or when giving the project to people who do not have the MSK addon. Previously, this shape key animation data would be lost, as it is dependent on MSK

Version 3.7

• Added code to FAQ that allows for removing long names created by grouping shape keys. Visit the addon's page FAQ and read the instructions
• When you have 2 shape keys with the exact same name, selecting that shape key will bring up a warning (normally it would happen when making a new shape key with an existing name)
• Other minor bugfixes

Version 3.6

• The mysterious bugfixes
  

Version 3.5

• Fixed folders not deleting in certain situations
• Updated sorting algorithm for decreased latency and faster speeds

Version 3.4

• Bugfixes related to SKC
  

Version 3.3

• You can now duplicate a folder and its entire shape key contents with the 'Duplicate' button in the drop-down menu

Version 3.2

• Fixed selecting a new shape key when removing a shape key
• Added a feature to allow the UI to display 2 shape key 'values' side-by-side, when those two values are made by Vertex Group Keys

Version 3.11

• Allowed user to add/apply Modifiers shape keys

Version 3.1

• Major code overhaul fixing issues like stability, performance and usability
• Refresh button removed, while fixing the problem of shape keys not showing up on 1-st time install
• Targeting folders now can be directly done in the list, instead of under it
• Working with the UI now feels smoother and accurate
• Minor bugfixes

Version 3.0

• Rewrote parts of the 'folder structure' management code to make it more stable and consistent
• Enabled editing the name of shape keys and folders by double-clicking their entry in the list
• Removed the ability to trigger an error by trying to remove a shape key when there are no shape keys
• Added a 'Refresh' button to update the list and show any shape keys that were in the model before the script was loaded
• On 'exporting' the model the shape keys' names no longer default to their auto-generated names
• On 'exporting' the order of the shape keys is maintained, so long as the folders are open