World persistency would increase usability since old in-world settings could load automatically when the user re-visits the same world later.
As worlds get more and more complex, this is no longer a "nice to have" feature - it is now absolutely needed to make a more complex world playable (such as playing a long story through like "The Devouring" for people who don't stay 4+ hours in a single world in VR or in case VRChat crashes while playing it).
But it is also needed for grinding mechanics and worlds where you can build something and farm resources - something we are currently working on.
Tl;dr, either VRChat gives us a [StoreToDisk] string datatype (without a weird character limit) that saves to disk when it changes and loads again when the user joins the same world or we'll have to implement our own open-source solution reading debug log files and a third-party application running on people's PCs to send Ctrl+V to the window handle (as other world creators have already done it).
But either way, we definitely can't go on without a solution here and the current "ask a VR user to copy+paste a string" is not a good way to do it - especially since it's not crash-safe, so users lose all progress when VRChat disconnects the user randomly. But also since we still don't have a "Copy to clipboard"/"Paste from clipboard" function next to a TextInput field for whatever reason, something that would be extremely useful for VR users in general anyway.
Ideally, an instance could also specify to only load the progress from whoever created it, since it's not possible right now to know who's the instance creator in Udon, but that's only a minor follow-up issue.