Hi,
I´m corently learning SWIPL in university and I came through the same problem. I asked my professor and now I know how to solve the problem.
If you click in the right bottom where Prolog is written it will open a searching bar and some options. Click on "Configure File Association for ‘.pl’ ", i t will open another searching bar where you must search for ‘Prolog’ to define it as the .pl language.
2 Likes