https://i.imgur.com/2SPTZbR.png
As you can see the Center options are greyed out with a layered group selected. When clicking on the individual layers it works though.
Viewing post in Center Image in Aseprite comments
I see your point, the extension works on the selected cells - you’d need to select all layers/frames/cells you want to center. And note, each one of them would be centered separately.
I designed it this way to follow the native UX of Aseprite and how it handles actions that move content like flipping or rotating an image. I’m honestly not sure if any Aseprite actions work if you select a layer group on it’s own.