Sign in as different user

16/02/2016 11:07

Go to the location C:\Program Files\Common Files\microsoft shared\Web ServerExtensions\15\TEMPLATE\CONTROLTEMPLATES.

Here we have a file named welcome.ascx.

Put it somewhere between others SharePoint menu items

<SharePoint:MenuItemTemplate runat="server"
  Text="<%$Resources:wss,personalactions_loginasdifferentuser%>"
  Description="<%$Resources:wss,personalactions_loginasdifferentuserdescription%>"
  MenuGroupId="100"
  Sequence="100"
  UseShortId="true"
  />