Editing of styles while writing is a two-part process.
Firstly, the style tag gets expanded (or we can also say "deconstructed") in basic tags. This happens independently of whether tags are displayed in the source pane or not. It is important to understand that, when the style is "expanded" in its basic tags, it is not a style anymore, but just a series of tags.
This has no particular meaning when you are creating styles from scratch, but it is very important when you are modifying an existing style. In the latter case, GN4 "saves" the style data, to be able to propose them when you make a change. Thus it is absolutely recommended that when modifying an existing style, you do all the changes on the paragraph before clicking the style edit icon.
Important precautions
•When modifying an existing style, do all the changes on the paragraph before clicking the style edit icon.
•Should you forget that simple rule, and click the style edit icon before you made any change, click Cancel, make all required changes, and then re-click the style edit icon.
•When you start to edit a style, finish it and save changes by clicking on the style edit icon, before you go to another style. Do one style at a time.
•Should it happen that you clicked the style edit icon by mistake, so the style was expanded, click Cancel. This will restore the style as it was before being expanded.