Regarding the "Subtract from next month's budget" or 'Subtract from next month's category balance" options for overspending -
It would be really great to have the same option for positive balances, for situations where, when one over-budgets, one wants the remainder to roll back into the pot rather than accumulate in that category.
For example - I save monthly towards my car insurance. This works great as is, rolling forward to accumulate towards a goal. On the other hand, I also have a cellphone with a bit of unpredictability... one month it's $41.32, the next $39, and so forth. I budget $42 to be on the safe side, and the fraction remains. Another example - I have a family member who doesn't want to participate in the budget, so I can't predict their expenses. I have a budget line that I toss $200 into, knowing through past experience that that will pretty much account for the charges I don't know about that will show up when the credit card arrives. If they come in at $180, I don't really need that extra $20 to roll over into the next month.
If I could select 'Add to next month's budget', or its equivalent, to have it added back into my total available for the next month, that would be well near perfect.
At the moment, I deal with this by going back and changing the budgeted amount, but that makes invisible in reporting, all those wonderful times we came in under-budget in a certain category (if I backdate the budgeting), or make it look like my cellphone costs less than it does (if I diminish next month's to compensate)