Holds screen in place

Windows installed in a house built in 2000 as a builders spec home. Sorry I don't know the brand of the windows but these plastic pieces are about 6 inches long. In the attached photo one view is facing upside and the second is the underside. The bottom fits in a groove of the window. The screen rests just over the slight edge of the top. I do not know if they were meant to go he entire width of the window or not. I have two measuring six inches each that can be placed anywhere but my windows are always filled with bugs. So I typically keep them closed. Many of these pieces have cracked and broken, but if they are reasonable enough I may replace together me by before I replace all of the windows. Help please!

Thank you for this suggestion I really am not sure how I could make this work but thanks again.