I really want to make magic arrows or silver caltrops or something, and I have! But when I make a new magical arrow, it must be made into a wonderous item, even though if I select a magical arrow to base it off of, it doesn't have that on by default. Even when I do make it a wonderous item, there's no way to make it stackable like how arrows can be, within ones character sheet. Is this even possible? If not, can there be an update in the homebrew item creator so that this can be done?  As it stands now a player would have to edit the weight of the name and the item themselves, which feels pretty clunky compared to just checking off a box in the creation menu for the item like:

[✓] Stackable?

or something like that. There's many changes that could be done to homebrewing on dnd beyond to make it much better but I think this is a simple one that could more feasibly and easily (i imagine, at least? but im no programmer) be implemented.

to the best of my knowledge, currently this cannot be done.  One cannot homebrew custom ammunition without making it a one-off Wondrous Item.  Just one of the many and manifoldly multitudinous ways in which DDB's homebrew tools suck donkey rocks.