Hello!
The way this is meant to be implemented is with inline tags!
<readDelay=x> will change the read delay value mid-string, so this is probably what would be most helpful. Use </readDelay> to return the delay back to a default value.
<d=x> will insert a single multiplier to the read delay (eg. if your delay is 0.1, typing <d=7> will produce a 1-time delay of 0.7) You can also define preset delays in the text data editor (the [T] icon in the top-right of any STM component) so if you're using the same delay over and over again, you can define it there so you don't have to edit your entire game script to make a programming value change.
The tags let you do a lot of mid-string programming, so I hope they're useful in this situation!