I currently have a monthly payment of fixed amount that every month needs a description like "Payment for 06-2019" where 06-2019 is the month and year. This is required by my biz partner to keep track, but also provides me with an overview which payment I already made.
Because all scheduled payments clutter the event overview, I have either the choice to do this every month again, or clutter my event list with an amount of scheduled payments.
Monthly recurring payments would be the solution for me, if one could use %M-%Y as a format string, and the description would adjust accordingly
%L would be last month (and change %Y to last month's year if it's January), and %N is next month.
If formatting sounds to complicated, just add a checkbox "append MONTH-year to description" with a combobox "Last / current / next month", cuz that's most likely the most logical changing or used months (one pays fees or rent usually for the last current or next month)