You have InDesign CS5, and you want to share the file with a designer using InDesign CS4. But in trying to export to an InDesign Interchange file, you find the .inx method is not there anymore. How is it done now?
Here is the new way. Try File > Export > InDesign Markup (.idml). This creates a .idml file (really, a zip file). In InDesign CS4, choose File > Open, then browse to the .idml file, and it will open and reconstitute itself in CS4. Be aware that some of the newest features of InDesign CS5, like paragraph spanning, won't survive the downgrade to InDesign CS4, but most of what you usually do in day-to-day work will translate perfectly.
If you want to downgrade the file to CS3, you must first open the file in CS4, and then again export to InDesign Interchange (.inx) and thereafter open that .inx file into CS3. My other article on this website tells how to edit an .inx file to open in even earlier versions of InDesign.
I tried, so far unsuccessfully, to rename the .idml file to .zip; extract the contents; and then see if I could code my way into a .inx file, but, no. Maybe someone else with more experience will figure out a way!
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