welcome to scirra. let me start by saying the 's' plugin is one of the more difficult things to use in Construct, and if used incorrectly, can cause crashes. Not trying to discourage you from using it, but in general, Construct is more intuitive and user friendly, so to make like easier, make sure Construct can't do it without 's' first, as it will probably be easier to do and more readable. Also, I've never used the built in save features on Construct. There very well may be a much simpler ways to do this, so if no one else replies here, you might try posting it as a general question in the help section.
But, back to your question
if you made a number array called, "layoutnumber", and a string array called "layoutname"
this would work:
you can name the arrays whatever you want,
but if you use layoutnumber wherever would normally use a number or equation, it will replace layoutnumber with the actual numerical value at runtime, and likewise with the layoutname wherever you can input text
so if you were on layout one and
set global('example') to layoutnumber + 4
global('example') would equal 5
or you could
Set Text to "hi, the name of this layout is " + layoutname
to have the name at the end of the sentence
these are System Expressions, and you get a list to choose from if you doubleclick the system icon while setting the parameters in any new action, condition, or expression