Thank you for your post.
If you're using a newer version of PlusSpec (v18.0 or above) there are new Window & Door Tools which allow different shaped windows (similar to the one you're after) to be added into a wall. In the latest version (v19.0) there were changes so these tools along with all the other tools work more efficiently and quicker than before. For any option that can't be done in the dialog (like the gothic head), we recommend to use whichever window is closest to the result you're after (in this case it'll be the 'Arch' window), then draw in the detailed header feature using SketchUp tools.
I'm not able to see the post you're referring to, however, there are some window types (e.g. the 'Custom' window) in the Window Tool that allow the number of horizontal and vertical panels to be entered, which will be spaced out evenly. There are also some options in the Door Tool.
Would you be able to please let me know if the above works for you?