Take screenshots that float over the screen, they will be non-existent to the cursor. You can select the elements in background.
Anytime double press the 'Alt' key or double click on systray icon, capture an area of the screen. You can change the screen and carry on with your work, captures will float, you will see them, but they won't interfere with your mouse.
Make multiple captures, move and resize them as you want. Save your captures or load images as new ones.
Select an opacity level for your captures.