v6.2.1.0 adds shortcuts for ABLoop
1. Clear All Markers
2. Set a Single ABLoop Marker (pressing the shortcut will 'Clear All Markers' before setting the start point, and pressing it again will set the end point)
3. Set a Single A-to-End Loop Marker (set the marker ends at the end of the video)
4. Start/Restart ABLoop (if there are more than one marker, 'Loop All Markers'' will be set)
5. Stop ABLoop

You can set them in Manage Extension Shortcuts

v6.2.0.3 - v6.2.0.5
- Updated code to support the new ugly UI of YouTube Player
- Adjusted zoom (Shift + Scroll) handling to be compatible with the new YouTube player UI
- Added Shift + Ctrl (or Shift + Option on macOS) + Move for axis-locked (constrained) movement