1. What is the issue? Please be detailed.
I’m using this process to automate syncing of an XLSForm and its required media attachments on ODK Central. I’m using this Form as a To Do Task Manager and it will upload a new Form definition anytime there is a change to reflect the changes on another system.
Currently I’m only using this on an XLSForm that is only 40KB. It is uploading based on a trigger, which could be a dozen times a day or more. While this is fine for a smaller form, for a bigger form (200-500KB) that is syncing 50+ times/day, this could add up. As this is an indefinite timeline and not a project that has a specific end time, the space taken up on a server over time for old published form versions could get bloated. Ideally I’d still be able to keep the trigger based on any changes so I can see changes close to immediately would be nice, but in my mind, the simplest solution would just be to set the trigger on a daily schedule or less frequent. However, this is unideal. Is there any way to delete old published form versions on Central that doesn’t involve deleting the entire active form?
I didn’t see anything in the docs and the AI search didn’t pull up any way to delete old published form versions.
No, there isn’t as far as I know. In the database, each submission is linked to the specific form version that was used to make the submission. That’s by design, but the consequence is that all form versions are being kept around, and so are their attachments (though deduplicated I believe).
It is, however, technically possible to have (and even use? I’d have to check) forms that don’t have all of their stated attachments. And it’s attachment bloat that is your problem, right? Technically, one could remove attachments of old form versions, of course providing that one is very sure that they won’t have a need later to answer questions such as “oh wait what picture did we actually show in the form version back when this submission was made” because of course that picture attachment is now gone. Deleting old form revision’s attachments is not likely an action we’d want to make available, not even behind an “are you sure” dialog. I’m just saying that if one is sufficiently motivated, I think it could be done, and my conjecture is that things will keep on working 
There is a somewhat similar story for the .xlsx files. AFAIK Central only uses an .xlsx once: to feed it to the converter, which produces xml. And then Central stores that xml; it’s the thing it’s actually interested in. The .xlsx is mostly just there for the user to download if they lost it (or if their organization lost it). If you were to delete the .xlsx from Central’s DB afterwards, all that happens is that you won’t have the download button for that .xlsx anymore on your form admin page. So depending on circumstances which may or may not be your circumstances, no harm done.