Hi. I know the Rock, Country and the Blues courses have a system of progression. Starts with course 1, etc. You can move thru the 'chapters' taking the lessons in order and they build pretty logically in my opinion. The instructors will point out that there are Rock Courses coming to replace the Rock Primers, but the primers are great.

What I have seen of some other lessons, Metal, for example, are not yet laid out in a progression exactly like that, however you can search and filter on the large collection of tutorials by difficulty. That's probably where I'm heading next. (Can't stand the screamin' but I love that "chunky death" sound!) ;)

As far as bookmarking, not an integrated system that I have found, however, I'm going fine just using my browser book marks. I like to keep the main page for the course on bookmark, then bookmark the current lesson I'm on as well and just delete the old ones as I move on.