I create a notification and specify Text and Text Expanded. On OS 10 (Pixel 3XL, September 5th 2019 patch) the notification category is High, so the notification initially appears in the non expanded form, and I can toggle between non expanded and expanded. However in either format the Text Expand content is always shown. If I remove the assignment of Text Expanded, then the Text content is shown. On OS 6, it does show the Text content in the non expanded format, and then switches to the Text Expanded content when I toggle to the expanded format, so I believe that OS 10 is not following the expected behaviour. One other interesting point is that my Text Expanded content is formatted with embedded return characters, so nicely formatted over 7 lines, however when in the non expanded format, the content is only on the first line, and the return characters get ignored, and the content gets truncated, which is okay, as the first line of the Text Expanded content is the same as the Text content, so I still see the information I want in non expanded, it just has some extra content I don't want to see.