Hi, I'm not sure if you can do that in the main view of the develop mode. However, using the second monitor function (which will display a new window if you don't have two monitors) you may compare to a different image without exiting the develop mode
From the develop module
- Click on the second screen icon or F11 (Windows, don't know if it is the same in Mac)
- In the second monitor you can select "Grid" and choose the images to compare
- Select "Compare" in the second monitor
Any edit you perform in the develop module will show in the second monitor
If you have only one monitor, toggle between windows with F11