Unfortunately we determined this feature would require extensive work to implement, which we were not sure would be justified. Can you tell me more about your purpose.
The "thumb.visible" property sould be useful for me when my user apply text filters on photos thumnnails, but in my case i already use a db where i have filenames, so i query the db, clear and refill founded pictures. IMHO a filter "visible" on thumbnail should be faster then clear and reload picture.