I'm not sure about shutting off, but have you tried using the "sort" (by title or date) and/or the "search" in the upper right hand corner? That should help with filtering.
Are you using with or without logging in to your ArcGIS Online or Portal account? If logged on, if you have any "favorites" checked, those will also flow to the top. I haven't played around enough with Explorer to know how the different sharing options affect it (i.e., if not shared but you are logged in as you).
Just some suggestions. Maybe you can put in a suggestion for this option on the ideas page?
