The game only has weapon animation data for the first 93 items, and the last two of those are actually coded to draw the Atma Weapon at different lengths depending on its damage calculation. As such, if you try to use an item slot beyond 93 (the second shield) as a weapon, it will instead be reading monster attack data or coliseum placement data, both of which risk having unstable pointers when interpreted as animation data.
https://www.ff6hacking.com/wiki/doku.php...ation_data
If working only with an editor, you won't be able to add any new weapons... you'll only be able to replace existing ones. If you're using assembly or a hex editor, though, you can relocate and expand the weapon animation data table...
Code:
C1/9DB8: BF 00 E4 EC LDA $ECE400,X ; weapon animation data
by changing this table load to a different address in the ROM and reading from the table there. Note that this table would require 0x800 contiguous (2048) bytes, and you wouldn't be able to edit it directly in an editor... you would only be able to make an animation and then copy it over to your new address.
Such a table wouldn't address jump and throw animations either, which are handled by a different table at D10400. Luckily, that table has enough entries for every item slot, so you need only update the values in a hex editor to adjust your new weapon's animation.
https://www.ff6hacking.com/wiki/doku.php...throw_data