Move the Anchor Point of the magnifying glass layer to the centre of the glass. Apply the Magnify and Bulge effects to the layer you want to “magnify”. Create an expression for the Bulge effect’s Bulge Center parameter and use the Pick Whip to link it to the magnifying glasses Anchor Point parameter. Do the same for the Magnify effect’s Center parameter. Now when you change the magnifying glass position the magnify and bulge effect will follow along.
Let me know if you need more detail.
John Dickinson
Motionworks
https://www.motionworks.com.au