If they can’t be taken off from inside then 2 things have worked for me…sometimes I can slide a putty knife between the screen frame and outer frame and release the pin. You could also loosen the screen spline about an inch either side of the pin and slide a screw driver in to release the pin.
Skreen Out screen removal tool (is not a prying tool.)
Most of time you are able to slide between then behind screen pulling from window frame.
(When having tight fitting screens)
(It’s best to actually use a prying tool in combination with the Skeen Out screen tool.)
Make the gap between the screen and the window frame.
To be able slide the screen tool behind the screen so to pull out.
Continually using Skreen Out like prying tool (which it is not designed to do), (will result in weakening and flexing of blade at end tool.)
(What it is designed to is), get screen out without bending or damaging window frame or screen.
(From your customers view)
Look more professional using Skreen Out less likely to scratch or bend there screens and windows frames.
Instead of coming in with screw drivers, paint tin openers, paint scrapers etc.