The Auto Adjust Split Transactions setting is supposed to auto-fill each additional split “with the current remaining amount.”
This setting doesn’t work for me. In the screenshots below, I tried entering the same split transaction with the setting turned off (left) and turned on (right) and there was no difference in the behavior of the split transaction dialog box.
Maybe I still don’t understand what this setting does. Maybe it doesn’t work in my browser. Maybe this works only works on Windows, not on Mac. All I know is that no matter what I tried, I couldn’t make this setting do anything different than what YNAB does by default.