Workflow Actions Out-of-box
SharePoint Designer supports only a subset of the workflow activities available from the workflow foundation. The two most notable workflow activities that SharePoint does not support are the WhileActivity, which is responsible for looping, and the ReplicatorActivity, which is responsible for iterating through a collection. Other activities, though supported, have limited functionality. For instance, the LogToHistoryActivity, which is used to log messages to the Workflow History list, cannot write to the Other Data field; therefore, messages from a SharePoint Designer–created workflow sent to the Workflow History list are capped at 256 characters. If the limitations of SharePoint Designer are too restrictive, Visual Studio is the answer. With Visual Studio, you have complete access to the capabilities of the SharePoint Workflow host and workflow runtime. The designer in Visual Studio allows for looping and iteration—the two key reasons why most solutions require a Visual Studio workflow. We need to go for creating SharePoint Custom Workflow activity when SharePoint designer does not support out-of-box inbuilt actions for workflow. We had requirement to add/create new item in sub site's list when workflow is triggered. SharePoint designer workflow actions support adding item in same site list but when it comes to adding item in sub site list it doesn't support, so we need to create SharePoint Custom Workflow activity. Let's see how can we create Custom Workflow Activity: