Bookmarking is already in the Adapt Authoring Requirements Mindmap for version W 0.1 of the Adapt Authoring Tool.  The sign off for this document is June 3, 2014 according to to the Requirements and Design Documentation Summary.

Requirements -> Adapt Authoring Tool -> Roadmap -> W 0.1 -> Content Creator -> tracking -> CCR-TRK-005: Able to toggle bookmarking (returning users to the location from where they exited the last session