filetypes and Insert Child / Sibling dialogue

With well over 1,000 .dita files under my belt working in another environment, I thought I'd give structured FM another try.
Quick question from this afternoon's experiment … an Insert Child / Sibling > topicref dialogue that blandly defaults to an empty list of .xml files requires three extra clicks every time I try to select one of my existing .dita files. This will swiftly become tedious. Is there a way of setting the preferences so the default file-extension for this dialogue is .dita? or even 'All DITA documents', which is already an option for the File > Open dialogue.