I'll assume you have the Aus Essential library, in which you have the louvre window, which under "general settings" has a parameter called "Number of units" which will split the window into the number set.
So all you have to do is set it to the overall length you require, then set the number of "units".
Schedules as a single window.
Unfortunately you can't set individual lengths for each section, so if you have sets of louvres of differing lengths you'll still need to do them individually.
Also it doesn't allow adjustment for load bearing columns between the window sections.