Not sure exactly what you mean, but I would say more like a PDF viewer. You have a section to the left side with two tabs. One for the search feature and search results and the other tab for an outline with bookmarks at each article. So for the NEC, the outline bookmark has each article of the NEC, the Chapter 9 tables, etc. You can adjust the size of this side section to however small or large you would like or even hide it entirely. I did this on accident, but it acts similar in that fashion as Bluebeam Revu’s sidebar if you are familiar with that one.