You need to use the old style mixed interval budget to be able to set a budget that hold the values indefinitely or for the time you set. The new style can only be copied from the previous month, so to fill a year you have to go to each month and copy the previous month one at a time. Also you will find the old style budget is much faster to navigate.
Another hint on using the "old style" which is far superior to the new one is set your budget amount to a daily figure, this will commute to a yearly figure on your budgets and will be 100% accurate setting a yearly figure seems to not calculate correctly example would be say $1 a day budget amount would equate to $365 a year
Probably the best way to bump the budgeted amount for any category for a specific month is to add another entry for the same category to include the additional amount for that month.
01-01-2018 thru indefinite, Insurance, $100 monthly
12-01-2018 thru 12-31-2018, Insurance, $50 monthly (additional amount)
If you run a report for that period you will see that all months have a $100 budget except December which will have a $150 budget.
Only issue I find is having to add that additional amount to your budget for each year.