Sectionalizing is something I do in my scriptures all of the time. It is so helpful for me to pick out major themes and doctrines that are being taught. Sectionalizing is when you draw lines in your scriptures to create “sections” or groupings scriptures that are talking about the same theme. For example: in the first section you would draw a line above the first verse and then another line below the last verse. And then you would write the given phrase in the margin between those 2 lines. You can find an example here.
So here are the sections for the Book of Mark.