So I have lots of reoccurring expenses which are often split (sometimes it is a business expense, which is split between a tax-deductible account and a non-deductible account, or a joint expense, where half of it is an expense and half a credit to an asset account representing the money owed), but while the amount may change, the percentage split doesn't. So auto-fill works great for getting the accounts I need, but once I enter the new total amount, the splits are all wrong and I have to manually adjust them. It would great to have gnucash auto-adjust the split amounts after an auto-fill and total change, to keep the same percentages as the old transaction had. A quick example for illustrative purposes:
Say I am updating my Credit Card Liability account. I have the following transaction:
Business Lunch $32
Expense:Business Meals $24
Expense:Lunch $8

The next week I have a similar lunch, but the amount is $40. So I type in Business Lunch, GnuCash auto-fills the transaction and then I type in $40 for the total. I'm left with:

Business Lunch $40
Expense:Business Meals $24
Expense:Lunch $8
(Unaccounted-For) $8

It would much more efficient if, when I entered $40, GnuCash adjusted the existing splits to:
Business Lunch $40
Expense:Business Meals $30
Expense:Lunch $10
So the percentages stay the same, but the values are adjusted based on the new total.