This add-on retrieves and stores the positions of selected bones relative to the highest selected bone in the hierarchy (usually the root bone) in order to later set these positions without affecting the root bone. In effect, this allows for animations to be seamlessly looped whilst making an animation using root motion.

Install like any zipped blender add-on.

To use, in Pose Mode select the bones you want to apply to on the first frame of your loop, go to the top bar menu and click the "Pose" -> "Animation" -> "Get/Set pose offset" and select "Get offsets". This 'stores' the reletive offsets of the selected bones, with relation to the topmost selected bone in the hierarchy (eg root). To set the bones to this position again, use the "Set offsets" button while on the last frame of your loop. The pose will now match the first frame, but with any locarion changes the root bone underwent.

This is only a tiny addon, but if you can think of anything that might make it more useful, feel free to let me know!

Also dont forget to check out the Root Motion Looper on Gumroad (veethegator.gumroad.com/l/arml) for a PWYW version :3