TL; DR A year ago, I took to AWS to solve a label ordering challenge in my productivity application Todoist. I’ve summarised it in this project page along with the outcome of this addition.
I recently revisited to see if the REST API was updated to allow reordering of items. It had not. The relevant property was read-only, and therefore, the functionality was still exclusive to the Sync API.
I took this as an opportunity to learn the Sync API for which there was an official Python library.