Set the variable 'clip_filebrowser' and you will be able to browse. This variable is found under Setup > User Preferences - Browser - category. Originally posted in cdnusers.org by Padmin
If you want to only look in a specific location, modify your 'clippath' variable setting to point to the specific location of your sub-drawings. This is found under Setup > User Preferences - Config_paths - category.
Have fun! :)