Context
The first step for document structure management is to introduce the ability to modify the document organization. The alternative would be to introduce Structure first but that would be inconvenient to have the Structure but without the possibility modify it.
Reorder in Table of Contents
Design:
The Table of Contents (ToC) part is enlarged by default to give more space for longer titles (and, later, hierarchy). The Table of Contents can also be collapsed for people who want to focus on reading the content. The ToC state (collapsed, expanded) is not persisted.
In the ToC, each title has a drag on the left hand side. The title can be reordered by drag'n drop.
Changes are done directly, there is no "Save" step.
There is an alternative to drag'n drop with arrows for cases where dn'd cannot be used by people.
Reorder is accessible to all users with the ability to modify the document.
Note: in a previous iteration of thought on the subject, we had in mind to have an "Outline view" to modify document structure.
Technical constraints
There is a need for a new REST route to reorder sections because the current PUT route would re-create sections and change the URLs (because new UUIDs will come with new sections).