Workflow task actions have been changed in SharePoint 2013 designer. Although you will not find an action to assign a to-do item in SharePoint designer, there is a workaround to achieve the desired functionality.
This blog will show you how to add completed or in-progress buttons to workflows.
Add a new content type
Go to site settings. Click on “Site Content Types” Under Web Part Galleries.
then Click on Create.
First, you need to add a new content type with a similar parent content type i.e. Workflow Task (SharePoint 2013).
Give your content type a name. Then under the parent content type section select “List Content Type” from “select parent content type form” and then “Workflow Task (SharePoint 2013)” for “parent content type” under List Content Type then hit ok.
Add a column to content type add a new site column to the newly created content type by clicking on “Add from new site column”
Give it a name and select Task Outcome as column type.
Add the option that you want for the button name (i.e. approved and rejected)
Add that content type to the task list
Now you that have added column to the content type. Let’s go ahead and add the newly created content type to the Workflow task list. Go to List setting > advanced settings and check allow content type management to Yes.
Now you will be able to see add content type under the content types grid. Hit add existing content type to the list. Add your newly created content type to the list and hit ok.
Since we are done with tweaking the list, let’s add a task. It works with both task actions in the SharePoint Designer.
In task properties go to output options and select your newly created content type and the outcome field (the one you added to the content type).
Create an item
To test your workflow you need to run the workflow. Add an item in the list (which is attached to Workflow).
Go to item workflow status.
Open task and edit it. You can see now you have two new buttons. In my case, they are “in progress” and “completed”.
Just like that we have created custom buttons to the workflow, it’s extremely simple! We encourage you to take advantage of this functionality and make SharePoint work for you. If you run into any issues or have questions about creating your own buttons, please feel free to let us know in the form below.