Good Day Ernest,
Thank you for the information. I look forward to learning more about your plugin.
Actually, I should apologize for not checking the HTML source code before bothering you with a trivial CSS question; however, I understood the interface depicted above (editor-css.jpg) actually inserted Inline style (using the style attribute) rather than style tags.
Just a friendly suggestion to eliminate ambiguity:
Your method of including CSS using the editor located at Theme & Styling > Custom CSS, is referred to as Embedded style in the US. Perhaps this is not globally accepted terminology; however, there should be a way to differentiate between the two implementation types since the true Inline style possesses the most specificity.
Regards,
Don