It would be a completely different item. Botania's Terrablade is just a Minecraft sword that also happens to self-repair (like all mana equipment) and that emits mana bursts similar to a man spreader with a damage lens.
From a brief check of the Terraria wiki, the much wider projectile would likely need some entity trickery to work as intended. Also, the attack itself would probably need to be a custom attack effect, something like a wider ranged sweeping attack at the player's position instead of the attacked target position. I guess it'd be more like a ravager roar than an attack with a melee weapon.
All the usual "I want to make a mod" prerequisites apply, like knowing/learning Java and setting up an environment for compiling a Fabric and/or Forge mod.