Here’s how to use it after installation:

Select the rig and switch to Pose Mode;

In the side panel, choose the Action you want to modify from the dropdown menu;

Select the corresponding Action Slot (the add-on will show its users for clarity);

Define the frame range where the offset should be applied by entering the start and end frames;

Click the “Offset” button. From now on, any transformation you make to the pose in the viewport will be automatically applied across the selected frame range!

Important: If you want to undo a change made while the offset is active, press Ctrl+Z twice — once to undo your edit and once more to remove the offset propagation.