Thanks for the feedback and making the video.
Unfortunately Apple's Mac App Sandboxing security system pretty much precludes this from being possible, at least on any app approved to be on the Mac App Store. Apps on the store like Hype cannot read files that you haven't granted permission to.
To even link to files at all, apps have to use a pretty clunky and fragile technology called Security Scoped Bookmarks (reasonable overview here). To be specific, while Hype does store a full path for some verification and bookkeeping, ultimately it uses this bookmark mechanism to find and read your file. Bookmarks have a couple levels in which it can keep track of your file and can survive some changes in the directory you make, based on how much time the app wants to spend looking for it. Hype goes a more minimal route for performance reasons. Regardless, the bookmark system can't capture the intent that you'd rather the file be relative to the document. This is just something Apple didn't really plan for. This would be a good feature request for them, but to be frank they haven't really made any improvements to sandboxing in ~10 years.
Thanks for the in depth explanation on this. Happy for this to be closed
@jonathan Would it be possible to add a "Reveal in Finder" option when right clicking on resources. That way it'll be easier to manage which resources are being used.
Yes, I think this would be a good idea. Just note that Hype works by storing copies of files internally, and only keeps a loose link to the original. A 'reveal in finder' would be to this original, which might have lost linkage at some point for a variety of reasons (copying to a different machine is the common culprit). If you want to edit files in Hype's control, instead you can use the "Edit" menu in the resources library. It will likely corrupt your document if you open the files directly within the .hype document while open.