I don't think something like that is possible in Ren'Py.
Viewing post in Lucky Paradox Enhanced Edition comments
there is, i have other games in Ren'Py and it basically works as a timer for how long specific text is displayed before progressing to the next text display. I don't know how to set it up, but from what i've seen in other games, it might be a variable attached to each text block that must be set independently. an example i've seen elsewhere has a section where if you don't read something quickly enough it vanishes in order to convey distress in one of the characters (although you can scroll back through in order to read it better). overall, if my guess is how it actually works, it would take a long time to implement at this stage, as each block of text to be displayed in game would have to basically be recoded, and that would be a nightmare.