Intuitive way of changing the y of block in a mine cart

this isnt really related to coding at all but i didn't know where else to put it. Basicly, in my plugin moreminecarts i have added the feature to set the blocks y, although i am unable to think of a way of changing this without having to use commands. i use when a player shift right clicks the minecart to set the block inside it so i cant use that. All suggestions are welcome!