In Onlymega editor it's possible to copy/paste items not only inside the banner but it's also possible to copy items from one banner and paste them in another banner.
1. Select one or multiple items:
2. Click Copy in top menu
3. Open banner where you want to paste copied items and click Paste in top menu;
As you can see - all items (text, buttons, shapes, images, animations) were copied to a different banner: