The bow-sword is required in the Devious Mindsquest, for the monk at the Paterdomus temple on the way to Canifis. Although the bow sword offers a wield option, attempting to do so produces an exclamation that "It's a bow and a sword...how am I supposed to use this?!" Asking the monk to teach the player how to use it produces the comment that "it's a foreign weapon" and "perhaps later" one of their warriors can teach them.
Sir Tiffy Cashien states at the end of the Devious Minds quest that players will be able to learn how to use the bow-sword in the future. According to the monk, about it being a foreign weapon, seems to hint at, if the player does go about learning how to use the bow sword, it will likely be a quest involving the Eastern Lands.
During the player encounter with the assassin during Temple of Senntisten they are told, if they chose to ask, that if they want a bow sword they should look into the sacred clay weapons from Stealing Creation, which can be morphed into all 3 types of weapon on the combat triangle. The conversation resulting from the choice of that dialogue sequence seems to be a veiled dismissal of the possibility of the bow-sword ever being released for player use, as the sacred clay weapons do essentially the same thing.
In the player-owned ports minigame, while someone's ships are away it is possible that they'll get the message: "Your ship traded for a crate of swordbows. Sadly, a storm washed them overboard."