Adding this feature would let Krita become a more professionally viable animation software. It allows for animators to move the onion skins so that they can in-between their drawings in a custom position, allowing inbetweening to become significantly easier. This is a common practice, especially in the Japanese and Korean industries. There are two ways to go about this. Most of your current audience would prefer #2, but older, traditional animators are more familiar with #1: 1) (seen in Clip Studio Paint, Toon Boom Harmony) Ability to select a drawing, or the current image, and send it to a "table". This creates a custom onion skin view where you can transform those selected onion skins. 2) (seen in TVPaint) Ability to affect onion skin images's transformation within the existing onion skin view. https://www.tvpaint.com/doc/tvp11/index.php?id=lesson-tradigital-animation-advanced-classic-tools-oop https://docs.toonboom.com/help/animate/Content/HAR/Stage/005_Traditional_Animation/272_H2_Shift_and_Trace_.html
You can view animators performing this technique (in Japan it is known as タップ割, Tap Wari) in the following videos: https://www.youtube.com/watch?v=Z5hXLWQz_VQ https://www.youtube.com/watch?v=ox8WDcRjdbw https://www.youtube.com/watch?v=CiF07Nj6N7k
This feature is being discussed in this thread for future reference https://phabricator.kde.org/M148 The workflow might be a bit different than other tools,but it should solve the issue with moving other frames around to help draw a new one