Installation

Installation here is standard. Go to menu Edit->Preferences and click Add-ons. Here click Install.. on top of the window and find downloaded file in a browser. Click Install Add-on and click checkbox to run plugin.

Main Button Groups explanation

1. Onion Skin

 Toggle Onion Skin

Toggle Fade Layers

Toggle Lock Inactive layers

2. Navigate

 Go to previous keyframe

 Go to next keyframe

 Go to previous frame

 Go to next frame

3. Keyframes

 Add new blank keyframe  

If there exists frame in timeline, new keyframe is placed on current frame with shift of other frames (standard behaviour) or is placed after current keyframe. You can choose option permanently in addon preferences:

Duplicate keyframe 

Clean keyframe (button hidden by default)

Delete keyframe (button hidden by default)

4. Layout part

 Focus on 3D View window (CTRL+SPACE function)

 Center the camera view and fits to its bound (HOME function)

 Top header (toggle between 3 states - Show Header + Show Tool Settings -> hide all)

5. Undo - Redo part

 - Undo

 - Redo

Onion Skin switcher

You can select up to 4 frames forward/backward to be visible.
Double selecting of one of the levels switch off onion skin for selected direction. 

Extended options for managing frames

Active frame options:

• Make Duplicate - duplicating keyframe - If there exists keyframe in timeline, copied keyframe is added after the source frame and has the same duration
• Clean - removes drawing from keyframe
• Delete - standard delete
• Delete and Slide Off - deletes keyframe and shifts frames to keep duration of previous frame

Selected frames option (more planned):

• Set Duration - you can set duration of group of selected frames with one click
• Repeats - repeats selected sequence of frames - fast way to make loops
  
• Ping/Pong - repeats selected sequence of frames (not the last one) and inverts order - fast way to make back and forth loops
  

Toolbox panel

You can fastly change tool without manually changing of interation mode.

Also there is new option for sculpting only last (or last+) stroke .
You can run it selecting "Last Stroke" from the list.

By default it is shown now as a side overlay buttons:

If you prefer old-style Toolbox panel - switch off buttons in Add-on Preferences.

Drawing with Hints

Expected mode - shows next stroke as a reference to draw

Compare Selected mode - highlight strokes of previous and next frame which are equivalent to selected stroke in current frame

Consistent Stroke Selection - option
This gives posibility to focus on the same part of strokes (with the same order number) travelling through keyframes

References

You can add reference drawings/images and edit their properties straight in grease pencil mode.
Use buttons below for this:
- adds reference of drawing before current frame - with "before" onion skin color applied
- adds reference of drawing after current frame - with "after" onion skin color applied
- reference of current frame
- reference of selected part of current drawing
- image reference

Use this button to switch on manipulators for single reference you want to transform.

Known issues