How to remove these window screens?

Hello. Here is the screen:



Here are the bottom right and left corners, respectively:





These windows can be removed. I unlatched them, tilted them forward, and raised the screen up to the top of the window frame. Here's the top right of the screen. The highlighted part in the photo is blocking the screens from coming out forward:



Likewise, a similar piece stops in from coming out backward:



So how do I get these things out? Thanks.

How to remove these window screens?