As we previously covered, when a model is saved to the models folder, it will appear in the Models category of the Processing Toolbox panel. What we didn't mention earlier was that it will also appear in the Algorithms tab of the Processing Modeler window. This means that a previously written model can be used as an algorithm in another model.
Models won't appear as algorithms if some of their component algorithms are not available. This can happen if an algorithm provider is deactivated in Providers, and you can find this by navigating to Processing | Options. For example, if you have used a SAGA tool in a model but have subsequently deactivated SAGA tools, that model will not be available. As long as all the algorithms in a model are visible in the Processing Toolbox panel, a model will be available as an algorithm.
To demonstrate this feature, we will...
