Hi Melanie,
we will have a look into how to make this possible in the future. A way to copy content of a scene at the moment is to simply copy and paste it like text in a text editor.
1. While pressing "shift" select all content of the scene with the mouse.
2. Copy the content with "cmd + c" (Mac) or "ctrl + c" (Windows).
3. Open the other scene (in a new tab for example) and paste it with "cmd + v" (Mac) or "ctrl + v" (Windows).

But this just works with unlocked items. If they're locked, you need to unlock them first in order to be able to copy and paste them.

I hope this can help you for now. Let us know if you have any questions.
Thanks,
Benjamin