Is there an easy way to add rounded edges to semicircle in OpenSCAD?
I'm far from a wizard with OpenSCAD, but enjoy using the program, learning something new every time. In your case, it's likely that you can use the roundanything library to accomplish your objective.
The library will present various implementations in the samples, making it an exercise for the reader to determine which module calls will present the solution.
The image below shows a part which has had the radii applied in a manner similar to your image: