what operating system do you have, Mac or Windows?
In Windows, all filemaker windows exist within an application window. So far, I haven't found a way for a script to resize or reposition the application window, but I can use window script steps to control the size and postion of windows within the application window. There are get functions that return the size and position of your current window. There are get functions that return the the size of your monitor screen. Thus you can calculate window size and position specific to the current monitor. You can also use Resize to fit as a way to "snap" the window down to the minimum dimensions needed for the current layout.
You can't resize the actual layout objects but there are ways to set the window zoom from your script and you can set "anchors" on layout parts to get some ability (limited) to reposition and resize them in response to changes in the layout size.