What happens now when you drag a paragraph from one place to another is easier to describe than actually use in practice. Here we consider change.
The paragraph is moved from one place to another. Within a page, between pages, between sites, its always the same. The from and to sites are both forked if necessary to complete the edit.
Except if copying from a ghost page or from another page with the same name or holding the shift key down, then copy to new place even if it looks like a move.
Here we consider what is most often intended in categories starting with improving ones own work, acquiring the work of others, improving their work on their behalf, and then, probable mistakes.
Same page ➜ move it.
Between pages you own ➜ move it.
From a search result ➜ copy it.
From your history ➜ copy it.
From plugin example ➜ copy it.
From another's page ➜ copy and cite it.
From another's history ➜ copy and cite it.
From another's plugin example ➜ copy and cite it.
With another's page ➜ fork then move it.
From yours to another's page ➜ fork then move it.
Between another's pages ➜ fork both then move it.
Within plugin page ➜ return it.
From anywhere to a plugin page ➜ return it.
Once happy with every case we can infer rules that are easy to code and maybe easy to remember.
The consequence of the rules should be obvious. Copy leaves the original in place and hovers with a circle-plus. Cite can color the circle-plus with the source flag. A circle-cross might show moves to returned.
Modifier keys might override rules. Shift to reverse move/copy, alt/option to reverse citation.