Hey @y.winter 
Welcome to the Emma Community! You can introduce yourself here if you like.
I love it when we see people doing cool workarounds like this 
but yeah that is a nice idea to be able to switch symbols
What do you find is the main benefit for you for putting this as a future month? Do you want to categorise this spend as e.g. entertainment, but under the month that entertainment takes place instead of the month you actually paid for it?