Masterwork weapon quest should allow any normal melee or thrown weapon to be created as +1 with (special effect) in the blue flame forge. It's annoying to limit possible weapons to three which won't even be usable but for certain classes.
The furnace is bugged in my play through. Can’t craft anything with it. Keep getting “invalid combination” message. Sent in a report to Larian but have yet to hear back from them.