Tap pencil icon next to 'TIMELINE SLICES' in left pane. This will allow you to view the definition of your slices, add/remove people to/from slices, create new slices, etc.
From the profile of any user or list, there is an option to add to bookmarks. It is in the dropdown to the right of the follow/subscribe buttons.
You can also bookmark searches using the dropdown when viewing search results.