I want customize buttons of my form in a task in my workflow.Is it possible? which is the file that contain buttons's details of form-task (buttons like Rejected,Approved..)
In your share-config-custom.xml, that's where you define your form components. Then in your workflowModel.xml file, you define the list of buttons you want that are associated with your task and form definition. Here is an example from the workflowModel.xml file