Edit:
I figured it out. Use RCO Editor (bundled with CTFTool) to edit Text Data of the topmenu_plugin.rco file.
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It seems like info and tutorials have become scarce. I was fortunately able to recall what I needed to do, after spending time over the course of a month looking online. Thankfully the lightbulb went off! But I've forgotten as much as I ever knew about editing CTFs. Aside from searching online, you can ask for help in places like here and on Reddit, but it seems as though most of the people that could help with these things aren't in the scene anymore.
I want to know.