The Setup:

I was looking to see who had a weapon enchant that I didn't have. I clicked on the 'weapon' filter and all the Enchanting recipes disappeared; click on Enchanting, they all come back.

It appears that even though Enchants tend to have specific item slots they can be applied to, GuildBook doesn't realize this. It looks like the Recipe Filter is only looking at the filters from a 'crafted item' stand point. Example: Engineering -> Cloak, results in Parachute Cloak; Tailoring -> Cloak, results in Night's Eye, Glacial Cloak, etc. But Enchanting -> Cloak, results in nothing. Despite me having multiple Enchants for the Cloak slot.

This probably would require a running database that says 'hey, this enchantment can go here'. All though, it does look like the default Enchanting UI has a filter. So maybe the API has something that can be read.

NOTE: I mention other professions because I'm unsure which other ones have items that can be applied to item slots (ie Spellthread and Armor Kits; specifically Spellthreads aren't showing under Legs filter, but crafted Leg gear is).

those filters were added and the feature is kinda young, i would need to look at how i could scrap the info, if i recall enchanting 'slots' were awkward to obtain (at least from the enchant spell) maybe the recipe list is an option

i will look though