It appears that the list shows all files from the folder that is first in the "Schematic Libraries" list in the dialog "Project Properties".
To open "Project Properties" dialog box type ACEPROJECTPROPS or right-click Project in the Project manager and select "Properties..." at the bottom of the menu.
So you can create a folder that contains only the files you need and temporarily set it as the first in the "Schematic Libraries" list.
Regards,
Vladimir