Hello mulot, welcome on the forum!
Are the two characters also sharing the same skeleton or not?
In case they share the same skeleton, pay attention to not modify them, but import the skeleton in the project to have it twice, animate the hugs etc. then import the animations from the duplicate to the original once you're done.
In case they're two separate skeletons, just import the second skeleton in the first skeleton's project, when you export them you'll get two jsons, and everything will be fine.
To hide a l̶a̶y̶e̶r (no layers in Spine) attachment, click on the dot in the first colum of the tree, the one with the eye. Don't hide the slot, because it only hides what's inside in the editor, but not at runtime, or in the preview view.
You can see how at 0:37 of this video:
You can only copy keyframes to paste in the dopesheet, so if you want to copy an in-between pose, you need to create keyframes for that pose. you can do it quickly using the shortcut Ctrl+Shift+L
, that keys the current pose. You can learn more shortcuts at this page: Spine: Cheat Sheet
Don't worry 😃 your English was great! I hope you'll be able to create as many hugs and smooches as you want! 😃