when you combine an item with another item the only option is to create a new item. Which takes you back to the original problem
What i've done is created a blank frame and named it editorscreen, with a small function panel graphic in the bottom right corner. Ive made a hotspot in this graphic, and used a eyeball picture.
Now every new frame i make, im just going to dupluicate the editorscreen frame, add the actual picture I want as the frame background, and before I do anything else open manage inventory, drop the map onto the eyeball hotspot and use that to link it to my actual map frame.
Doing this means for losing 5% of my frame screen, and 10 seconds to make the examine function each time I make a new frame, the player can examine the map from whatever screen they are in (once they have the map as an inventory item!)
Not perfect...but cunning
But if i've overlooked something put me right please, for the little resources and time it takes I'd still rather have the magnifying glass over the map option.