Hi Thomas,
The workspaces for nested and anonymous functions are static. This means that all variables used within the function must be present in the text of the code. And there is no programmatic approach to find whether a workspace is static or not.
For more information on adding a variable to static workspace go through this documentation: Resolve Error: Attempt to Add Variable to a Static Workspace. - MATLAB & Simulink - MathWorks India
Hope this helps!