Given some existing Simulink files, there are several methods of fetching a list of toolboxes that the project is dependent on. These are listed below:
1. Using Dependency Analyzer
You can use Dependency Analyzer to see the list of required products.
To open the model dependency graph for your model, on the Modeling tab, click the down arrow to expand the Design section. Under Dependencies, click Dependency Analyzer.
Then, you can examine the list of required products in the Products section in the Properties pane on the right side of the model dependency graph.
Refer to the following link for the related documentation in the "Find Required Products" section:
https://www.mathworks.com/help/simulink/ug/model-dependency-viewer.html 
Note: Starting from R2023a, the Dependency Analyzer app seamlessly extends its support for the analysis of MATLAB files by integrating a dedicated menu within the MATLAB Toolstrip's App tab. This is equally applicable to Simulink model files.
2. Using the "dependencies.toolboxDependencyAnalysis" function:
You can use the "dependencies.toolboxDependencyAnalysis" function to programmatically determine which MathWorks products a particular Simulink model depends on.
Here is an example to determine the toolbox dependencies of the shipped Simulink model 'vdp.slx':
>> names = dependencies.toolboxDependencyAnalysis('vdp.slx');
>> names
names =
1×1 cell array
{'Simulink'}
In this case, the 'vdp' model requires only Simulink (and MATLAB as base product) but no additional toolboxes.
Refer to the following link for the documentation of this function:
3. Create a Simulink Project to use Impact Analysis
If your model is part of a Simulink project, use can also use the 'Impact Analysis' tool to find the required toolboxes for the project:
Information regarding the creation of Simulink Projects can be found here:
