gbavocab is a fully functioning 5-box vocabulary trainer for the Game Boy Advance. Load your vocabulary lists from a flashcard SD card and learn directly on real GBA hardware. Also compatible with dict.cc vocabulary trainer exports.

For adding or editing entries, gbavocab uses the same text-input controls as gbawriter, so consider learning the gbawriter input-scheme if you want to add/edit entries on the go.

With V1.60 you can also have your own offline dictionaries and add entries from there to your list. 

Code:
https://github.com/Xinon232/gbavocab

gbawriter:
https://xinon232.itch.io/gbawriter