Android running the latest beta.
In 31 a single tap on a highlight selected that highlight and in the context menu it could be changed or deleted. Now in the beta you have to drag to select the exact boundaries of the highlights to get those same options - otherwise you have multiple highlighting style being applied and no option to delete.
The real challenge with this is when you have two highlights of the same style overlapping each other. Swipe to Highlight is buggy and often stops highlighting to soon or too late, regardless of where my stylus is. So I often have a second highlight overlapping. Now I have no clear indication of where a highlight ends or begins and cannot delete them in the mobile app.