Said another way, allow for pending transactions to be edited.
Say I purchased fuel, and that transaction is pending with an amount of $1. I would like to be able to fill in the known amount (say, $40) and have that amount be reflected in totals and budgets.
If the posted amount differs from the previously anticipated amount, perhaps there could be a UI element similar to that of "marked as deleted" transactions that informs the user of that difference and asks them which value should be kept.
Related (to the idea of editing pending transactions):