Timeline will be in Redstone 4, it seems, and today's build adds the ability to more easily delete activities in Timeline and to sync activities to the cloud to enable better cross-device use.
Sets is similar to the recently introduced Stardock application called "Groupy." It allows users to group app data, websites and other information in tabs. The Sets feature is related to the Tab Sweep feature that Microsoft included in its Edge browser as part of the original Windows 10 Creators Update
Also new to Build 17083 are tweaks to make Windows Hello easier to set up; new modes -- and a new name -- for Quiet Hours (now called "Focus Assist"); and a new setting to turn on or off the ability to automatically hide scroll bar. Microsoft also is adding more granular controls over which Universal Windows Platform Apps can access users' pictures, videos and document folders. And there's a new Fonts Page in Settings as of this build.