I'm using SharePoint designer 2010, I have created 2 workflow (Workflow A and Workflow B), and now I want to call/start workflow B from workflow a. how can I do it?
When workflow A ends you can update a status column or a tracking column that will trigger workflow b to initiate. Prior to having a commercial workflow engine, I would have a main status column that drives workflow A and in workflow B, I'd have a condition like if Workflow A tracking column = X and workflow tracking column B = Y, do something. Else update a column so that workflw A refires.
In designer workflow, there is no option for calling another workflow... Refer this,
This provides you extra workflow actions like calling workflow etc.