This has helped me a bit as I work through problems. Paste your gcode, and it runs all the movements out graphically. Pretty neat. I had a problem with some gcode posting out of fusion (got another right now, lol) and this showed me where it stopped. Turned out I had an issue with the model somewhere on a part I had just made. So I backed up, did it again more carefully, made the toolpath, and posted.
Never figured out what the actual problem was or how I borked it, but this tool here gave me a clue. Also saved my bacon when I made a bunch of scrabble tile toolpaths and borked one of the names. The simulator is FAST, so I didn’t have to go re-post all of my toolpaths just to make sure they were correct.