So as with Some questions regarding Gwenview, I feel the need to answer this on two different levels.
To begin with, it feels like you’re slowly torturing your system to death by forcing the software to do what it was never designed to do, at the extreme limits of what it even can do. This method of using the filesystem to approximate a database–going so far as to actually use raw JSON code as the file and folder names–is almost certainly literally unprecedented.
It’s certainly very creative, and I’m somewhat amazed that it works at all, but I’m also not terribly surprised that you’re running into a lot of rough edges–as evidenced by the large number of questions you’ve been asking concerning edge cases and unusual usages. I strongly urge you to reconsider not only this method of organization, but also the logical chain of thoughts and decisions that led you to adopt it. I’m sure they each seemed perfectly reasonable at the time, but the place where they’ve gotten you to really isn’t. If you continue to use the system in this way, you’re just going to bang your head against ever more obscure quirks of apps that are being stretched far beyond their intended usage.
With that out of the way… yes, the rename dialog should ideally word-wrap at a certain point rather than just expanding horizontally forever, which is what it does right now. That’s a reasonable thing to request that a person could conceivably run into even with a more normal set of file and folder names. If you wanted to try, you might be able to use Window Rules to cap or fix the width of the rename dialog, but I can’t guarantee that such a thing is possible or would work reliably. Really, we should just fix this in the code for everyone.
P.S. you can use Emojis on a PC, either by, for example, typing “:thinking” (without the quotes) into this very text input field, or by using the KDE Emoji Selector window to copy the Emoji of your choice to the clipboard, whereupon you can paste it into here.