I always wanted to post here but I didn't know if you still check this topic and it can be considered necropost if I do.
But since you're here, so it should be all right.
Your script is really useful, and I've been using it for few weeks now. I admit, at first, I was confused with your instructions.
In this case the variable with id 4 will be changed to the input number.
The event will halt until an button is triggered, just like with RMXP.
Change the 4 to another number to store the input in a different variable.
I thought you meant each variable is used for the certain key. As like Variable #4 = Left key, while Variable #8 = Up key.
Of course, that can't be right. That would be too many variables and it's just not convenient. I had to ask another guy for help, and we had to test it in the game to figure what you really meant.
Maybe you could re-write the instructions to make it clearer? Just suggestion, in case other people thought same way I thought.
Other than that, it's marvelous script.