calcprogrammer1 started to work on a file browser that would support both slot-1 and slot-2 at the same time. Though it isn’t much, it can browse both slots (click the GBA or DS icons to switch slots). It can only be patched with one DLDI though (as all programs using libfat), so the SLOT2 device must be natively supported (GBAMP CF is what I have) and the SLOT1 device must have the DLDI patch.
Thanks to http://www.dev-fr.org for the news.