In the past I was used to use this feature, and copy some download apk to another personal directory.
Lately, in a different phone; Samsung note 4(android6) and external SD card.
I found out that this feature is not working, or I dunno know where to fin the apks…
I checked below paths without luck:
/storage/0000-0000/Android/data/org.fdroid.fdroid/files (external SD)