I believe this already exists in osrs but I'm not 100% sure.
While picking the herbs when they are fully grown your inventory will be filled like 3x, so you have to bank 3x. I know running to the bank is not that much of an issue at Catherby, but as for the Falador herb patches, the run is pretty long.
So my idea is, if you use any herb on the Tool Leprechaun, all those specific herbs will be noted in your inventory. Which will make picking those herbs much more efficient.
Again, this is not an original idea I guess. Just something which could make the gameplay slightly smoother.