How can I set page scrolling option for all files in a Ditamap?

Thanks so much for your prompt and precise assistance!

Winfried is correct; you need to set this in your topic templates so that whenever you open a topic from the map, you will get the desired view.

In the meantime, here is a simple script you can use that will change the setting on all of your open documents. To use it, copy the code and paste it into a plain text file and save it with a .jsx extension. Open all of your topics, and choose File > Script > Run and select the script. Alternatively, choose File > Script > Library and add the script to the Script Catalog and run it from there.

#target framemaker

main ();

function main () {
    
    var doc;
    
    // Loop through the open documents.
    doc = app.FirstOpenDoc;
    while (doc.ObjectValid () === 1) {
        // Set the page scrolling to vertical.
        doc.ViewPageScrolling = Constants.FV_SCROLL_VERTICAL;
        doc = doc.NextOpenDocInSession;
    }
}

I do not use DITA. Therefore my suggestion might be wrong.

I would recommend to set this in the template file. Possibly this will be used automatically or you would have to import this format into your topic files.