I don’t personally have too much experience with it but basically each time a script is updated, autocomplete callbacks (functions) are invoked, these functions can mutate the table (which is passed to the callback) that contains information about the autocomplete. That is to add or remove from the table, and this new entry will pop up in/be removed from the autocomplete box. I only really briefly played around with it but as I don’t make plugins, I didn’t make anything super in-depth. But it shouldn’t be too hard to write a simple command line script that lets you add a random test entry by registering a callback function.
It’s similar to TextChatService’s message options in that you can return an updated version of an old object to change the message’s behaviour and how it looks visually.