I assume that you added your support for drag and drop for bullets, because that would solve your problem.
One option for doing the drag and drop in a single .md file is to open it in Logseq. That allows you to drag and drop the sections and headings.
Quite a large number of Obsidian users have explained how they integrate using both Logseq and Obsidian on the same files. Though I’ve never personally enjoyed using Logseq, it’s clearly a good option for some.