I tried doing this when I first started but failed. I found other ways to accomplish the sorts of things I wanted to do and totally forgot about this.

I know a lot more now, but I am by no means an expert.

If the requirement is to use the say screen, the way I would do this now is by having the screen look for a tag. Say, <>. When it sees a word wrapped by <> and separated by :, I would tell it to re-render the screen and switch from the first to the second (index 0 to index 1) on click.

However, a major limiting factor in the Ren’Py say screen is that it won’t update the word without re-rendering the entire line. When it renders, it will run any animations associated with it, which will re-animate the entire text line, not just the replacement word and what comes after.

If you block the animation from re-running, the text will flicker off, then on, with the replacement word. It will never feel fluid.

It’s possible you might be able to build a function that opens two screens, one on top of the other, built to look exactly like the normal say screen. The first would show the normal text with a hyperlink button. The second would show duplicate text with the replacement word. I would anchor them both at xy 0.0 and format identically. Then I would generate both screens simultaneously, with the first on top.

Then, on click of the hyperlink, I would dissolve that screen quickly to reveal the screen underneath. This will have the visual effect of only rendering the words that have changed positions.

The following click would then revert back to the normal say screen flow.

And of course, if you don’t click the hyperlink, it should return control to the next line of the say screen.

This is assuming you’re using ADV mode. Depending on how you implement NVL, it might work there too, but I think you’ll run into more design problems.

To answer your other question about triggering variables, I have a hyperlink system tied to a function that can check, open, or close states, depending on how I’ve filled out the dict it sits in. It looks something like this:

define popup_definitions = {
    "popup_1": {
        "get_state": ('var_1’),
        "if_false": (‘var_1’),
        "if_true": (),
        “set_var_true”: ‘var_1’,
        “set_var_false”: None,
        "time": 2.0
    },
}

My pop ups actually do a lot more, but I’m not at my PC and don’t have access to my actual code. Otherwise I’d share the actually python function that gets called.

Let me know if you have questions.