In this blog post, I’d like to show you how to create a link to start Nintex Workflow Page in the document set home page.

1. Firstly, you need to upload the latest version of jQuery to the style library of your team site.

2. Then, upload a text file to the style library for writing your own html and JavaScript

3. In the document set home page, insert a new content editor web part and link the text file you just upload.

4. Update the text file with the following content, you can download this file here.

<script type="text/javascript" src="/Style%20Library/jquery-1.9.0.min.js"></script>
<script type="text/javascript" src="/_layouts/sp.js"></script>
<script type="text/javascript">
$(document).ready(function() {
    listItemId=getParameterByName("ID");
	setTheWorkflowLink("YBBESTDocumentLibrary");
});
function buildWorkflowLink(webRelativeUrl,listId,itemId) 
{ 	
	var workflowLink =webRelativeUrl+"_layouts/NintexWorkflow/StartWorkflow.aspx?list="+listId+"&ID="+itemId+"&WorkflowName=Start Approval";
	return workflowLink;
}
function getParameterByName(name)
{
	name = name.replace(/[\[]/, "\\\[").replace(/[\]]/, "\\\]");
	var regexS = "[\\?&]" + name + "=([^&#]*)";
	var regex = new RegExp(regexS);
	var results = regex.exec(window.location.search);
	if(results == null){
		return "";
	}
	else{
		return decodeURIComponent(results[1].replace(/\+/g, " "));
	}
}

function setTheWorkflowLink(listName) 
{ 	
	var SPContext = new SP.ClientContext.get_current(); 
	web = SPContext.get_web(); 
	list = web.get_lists().getByTitle(listName); 
	SPContext.load(web,"ServerRelativeUrl"); 
	SPContext.load(list, 'Title', 'Id');	
	SPContext.executeQueryAsync(setTheWorkflowLink_Success, setTheWorkflowLink_Fail); 
}
function setTheWorkflowLink_Success(sender, args) 
{ 
	var listId = list.get_id(); 
	var listTitle = list.get_title(); 
	var webRelativeUrl = web.get_serverRelativeUrl();
	var startWorkflowLink=buildWorkflowLink(webRelativeUrl,listId,listItemId)
	$("a#submitLink").attr('href',startWorkflowLink);
}
function setTheWorkflowLink_Fail(sender, args) 
{
	alert("There is a problem setting up the submit exam approval link");
}
</script>
<a href="" target="_blank" id="submitLink"><span style="font-size:14pt">Start the approval process.</span></a> 

5. Save your changes and go to the document set Item, you will see the link is on the home page now.

Notes:

1. You can create a link to start the workflow using the following build dynamic string configuration:

{Common:WebUrl}/_layouts/NintexWorkflow/StartWorkflow.aspx?list={Common:ListID}&ID={ItemProperty:ID}&WorkflowName=workflowname.
With this link you will still need to click the start button, this is standard SharePoint behaviour and cannot be altered.

References:

http://connect.nintex.com/forums/27143/ShowThread.aspx

How to use html and JavaScript in Content Editor web part in SharePoint2010