There's one category in my budget that, in my spreadsheet, is (unlike every other line-item) set to a defined percentage of my expected total income for the period. It would be nice if I could do this in Lunch Money as well, instead of having to update this line-item whenever my budgeted income changes.

I suspect this would also be useful for people who follow systems like "50/30/20" and "75/15/10" ...