Step 1: Create a self relation on the table which would be the basis of the link. In my case this table is InventJournal. So we create a new relation called AFZInventJournalTable and in this relation we link InventJournal with InventJournal as shown below
Step 2: Create a menu item with the url reference of the sharepoint page to be opened
Make sure to mark the WindowMode as Modal so that the page does not redirect to a new link and instead opens in a modal window.
Step 3: Create a Display menu item that will be attached as the edit menu on the list page. On this display menu specify the WebMenuItemName (created in step 2). This will inform the system about the webpage link to be used to open a new form in the Portal mode.
Step 4: Attach the menu item on the List form in the grid control, on the column to be marked for the link. Select the Display menu item on the HyperLinkMenuItem property of the column as shown below.
Step 5: Deploy the list page. If already deployed don't forget to deploy again and refresh AOD in EP.