Question: how do you cut 1/4 inch plexiglass?
Answer: I tape both sides of the plexiglass, the area where the cut will be, with old fashioned masking-tape (remember, both sides). I draw my cut-line with a sharpie on that tape. And then cut it with the jig saw. Without the tape, the plexiglass will melt, and your saw blade will get caught in the melted plexiglass.