Let assume 

Purchase Request - Main List

Request Team, Vendors, procurement department, PO are person/group ( allow multiple entries) fields in Purchase Request. Any other information related to Purchase Request (ex:category,location,request number) have them as separate sub lists and point them as lookup fields in Purchase Request.

Have a single Nintex workflow in Purchase Request and have separate custom buttons for each stage. On each button click update value to list field (ex:Status), have each status for each button. Based on each status hide other buttons for other users.

In workflow use 'Switch' case and implement your set of workflow actions. At the end of each branch set item permissions for each person so that they can have access to open item at equivalent stage alone.

Hi Lakshmi,

thanks for the reply.We have multiple list like.

Request list this is the parent list and below are the child list you can say.

Work Order

Purchase order

Now vendor will upload quotes in quotes list and workflow is running on request list so how to update status vice versa.

Each Purchase request will be having quote and status right. No need to update status in Quotes list.

You can select any of the quote for each purchase request from quotes list. (via lookup column in purchase request pointing to quotes values).

Is my understanding is correct.

Each Purchase request will have multiple quotes and requester will be approving a single quotes and after approval status of request to be changed.so there should be trigger point from quotes list to purchase request list.

Same way for the purchase order and work order, if any of the item changes in the list then parent Purchase request list status to be updated.

So there are multiple list and workflow is running on parent list,so how should be the workflow design.